Answer:
B. A shirt costs $15, and a pair of shoes costs $20.
Explanation:
Let s = price of 1 shirt.
Let p = price of 1 pair of shoes.
Adam:
5s + 4p = 155
Friend:
3s + 2p = 85
We have a system of simultaneous equations.
5s + 4p = 155
3s + 2p = 85
Rewrite the first equation. Multiply both sides of the second equation by -2 and write below it. Add the equations.
5s + 4p = 155
(+) -6s - 4p = -170
--------------------------
-s = -15
s = 15
A shirt costs $15.
Now we replace s with 15 in the first original equation and solve for p.
5s + 4p = 155
5(15) + 4p = 155
75 + 4p = 155
4p = 80
p = 20
A pair of shoes costs $20.