The owner of a bike shop sells tricycles (3 wheels) and bicycles (2 wheels), keeping inventory by counting seats and wheels. one day she counts 40 seats and 95 wheels. how many of each type of cycle are there?

3t + 2b = 95*
t + b = 40
t + b - b = 40 - b
t = 40-b Substitute this in the formula marked *

3(40-b) + 2b = 95
120-3b+2b=95
120-b= 95
120-120-b=95-120
-b= -25
-1b/-1=-25/-1
b= 25
Plug b= 25 into t + b = 40
t + 25 =40
t + 25 -25 = 40-25
t = 15
15 tricycles and 25 bicycles