Question

A store has a total of 15 bicycles and tricycles. There are 37 wheels. How many tricycles does the store have?

Answer 1

The store has 7 tricycles (21 wheels) and 8 bicycles (16 wheels)
21+16=37 wheels

Answer 2

x+y=15
2x+3y=37

15-x=y
2x+3(15-x)=37
2x+(45-3x)=37
2x-3x+45=37
-1x=-8
x=8

x is the amount of bikes, so there are 8 bikes. 8x2=16.
37-16=21
21/3=7

There are 7 tricycles.