Linda had twice the number of plastic blocks as Tommy. Linda used all her blocks to build 7 identical houses. Tommy used all his blocks to build 5 identical houses. Linda used 9 more blocks than Tommy for each house. How many blocks did Tommy have?

	Linda	Tommy
Number	7	5
Value	1 u + 9	1 u
Total value	7 u + 63	5 u

Number of plastic blocks that Tommy used for each house = 1 u
Number of plastic blocks that Linda used for each house = 1 u + 9

Number of plastic blocks that Tommy had
= 5 x 1 u
= 5 u

Number of plastic blocks that Linda had
= 7 x (1 u + 9)
= 7 u + 63

Linda had twice the number of plastic blocks as Tommy.

2 x 5 u = 7 u + 63
10 u = 7 u + 63
10 u - 7 u = 63
3 u = 63

1 u = 63 ÷ 3 = 21

Number of blocks that Tommy had
= 5 u
= 5 x 21
= 105

Answer(s): 105