small frames ($8): s
large frames ($15): L
Cost: 8s + 15L = 239 ⇒ 1(8s + 15L = 239) ⇒ 8s + 15L = 239
Quantity: s + L = 22 ⇒ -8( s + L = 22) ⇒ <u> -8s -8 L = -176 </u>
7L = 63
L = 9
Quantity: s + L = 22 ⇒ s + (9) = 22 ⇒ s = 13
Answer: 13 small frames, 9 Large frames
