12 - 5 = 7 Just like with addition, we can use a part-whole model to help partition larger numbers to make them easier to deal with in subtraction problems. First, partition 35 into 30 and 5.

Using addition and subtraction in multi-step problems. OLIVIA AND HASSAN:Ahh! Woohoo! HASSAN:Olivia, I think we're inside a computer. HYPATIA:How did you get here? This is the computer that runs ...