Task 1 of 2
On the "Quarter" sheet, in B2:B5, add up the January, February and March sales.
Lesson theory
A workbook can have many sheets: the tabs under the grid. To take a cell from another sheet, write the sheet name and ! before the address:
=January!B2+February!B2+March!B2If a sheet name contains a space, put it in apostrophes: ='Report 2026'!B2.
It is also handy to start the formula, switch to the tab you need and click the cell. Here it is easier to type the sheet name by hand.
Enter — commit · F2 — edit · F4 — $ in a reference · Ctrl+C/Ctrl+V — copy and paste · Ctrl+Z — undo
Esc or F6 — leave the sheet for the «Check» button · Shift+Tab in the first cell — back to the page