# Lesson 2-1

Fill in the unit box. Complete the fact extensions.

12-7= 120-70= 1,200-700= 8+3= 80+30= 800+300 6 + 8 16 + 8 56 + 8 14-9= 24-9= 54-9= Explain how you used a basic fact to help you solve Problem 4. Enter 33 change to 40 Enter 80 change to 73 Enter 80 change to 23 Enter 430 change to 500 Enter 700 change to 640 Enter 1000 change to 400 Add or subtract to complete these problems on your calculator. You may also use a number grid or base-10 blocks.

What combination of 10 helped you solve Problem 6? Explain.