You can add mathematical expressions and equations as floating objects on a spreadsheet. To add an equation, you compose it in the Numbers equation dialog using LaTeX commands or MathML elements, then insert it into your spreadsheet.
You can also add equations inline with the text inside text boxes and shapes.
Note: If you’ve installed MathType 6.7d or later (an application for composing math expressions), you can use it to create equations by clicking symbols and typing in the MathType window.
Do one of the following:
Place the equation inline with text: Place the insertion point in a text box or shape, or select the text you want the equation to replace.
Place the equation so it can be moved freely: Click outside the sheet to make sure nothing is selected.
Choose Insert > Equation (from the Insert menu at the top of your screen).
If you have MathType installed, a dialog appears, asking whether to use Numbers to create the equation. Click Use Numbers.
Enter an equation in the field using LaTeX commands or MathML elements.
For information on using supported LaTeX commands or MathML elements and attributes, see the Apple Support article About LaTeX and MathML support.
Click Insert.
Drag the equation to reposition it on the sheet.
If you have MathType 6.7d or later, you can use it to add equations to your spreadsheet.
Tip: To set MathType as the default equation editor, choose Numbers > Preferences (from the Numbers menu at the top of your screen), click General, then select “Insert equations with MathType.”
Do one of the following:
Place the equation inline with text: Place the insertion point in the text box or shape, or select the text you want the equation to replace.
Place the equation so it can be moved freely: Click outside the sheet to make sure nothing is selected.
Choose Insert > Equation (from the Insert menu at the top of your screen).
If you set MathType as your default equation editor, MathType opens automatically (after you enter an equation the first time). Otherwise, click Use MathType in the dialog that appears.
To enter the equation, click symbols and type in the MathType window.
For instructions on using the MathType tools, see MathType Help.
To save your equation, choose File > Close and Return to Numbers (from the File menu at the top of your screen), then click Yes in the dialog that appears.
Drag the equation to reposition it on the sheet.
To edit the equation, double-click the equation to open the MathType window.
After you add an equation, you can modify it.
Edit an equation: Double-click the equation, make your changes, then click Update.
Move an equation: Click the equation, then drag it from the center to a new location on the sheet or in the text.
Change the size or color of an equation: Click the equation, then use the controls in the sidebar on the right to change the font size, color, or alignment of the equation. If you don’t see the sidebar, click 
in the toolbar. You can also click a white handle around the equation and drag in or out to change its size.
Copy an equation: Click the equation, choose Edit > Copy (from the Edit menu at the top of your screen), then choose Edit > Paste. Drag the copied equation to a new location on the sheet.
Delete an equation: Click the equation, then press the Delete key on your keyboard.
Move a floating equation inline with text: Cut and paste the equation on the sheet into a text box or shape. See Place objects inside a text box or shape.