Question

A store sells small notebooks for $7 and large notebooks for $10 if a student buys 6 notebooks and spends $51 how many of each size did he buy

Answer 1

7+7+7=21
10+10+10=30
30+21=51

Answer 2

He bought 3 small notebooks (3*7=21) and 3 large notebooks (3*10=30)
21+30=51