Michael J. answered 05/12/16
Tutor
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Effective High School STEM Tutor & CUNY Math Peer Leader
If a certain number of apples are taken away, then you are losing apples in that group. When you lose objects, you are subtracting. Therefore, the number you started with in that group is decreasing. The subtraction you should have is
3 - 2
Imagine a standard number line labeled from 1 to 10. On that line, you start at 3 because there are 3 apples in the group to start off with. Because Joe took 2 from that group, you are going to count 2 spaces to the left from 5 on the number line. What number do you land on after you count 2 spaces to the left from 5? That number is the amount of apples that are left.