4s + 3p = 85.50......multiply by 3
3s + 5p = 115.........multiply by -4
----------------
12s + 9p = 256.50 (result of multiplying by 3)
-12s - 20p = -460 (result of multiplying by -4)
---------------add
-11p = - 203.50
p = -203.50 / -11
p = 18.50 <=== the cost of a pair of pants
3s + 5p = 115
3s + 5(18.5) = 115
3s + 92.50 = 115
3s = 115 - 92.50
3s = 22.50
s = 22.50/3
s = 7.50 <=== the cost of each shirt
