To determine the answer, we need to set up equations. We do this by doing mass balances. We let
x = A alloy 25% copper
y = B alloy 55% copper
Overall Mass balance:
x + y = 100
Copper mass balance:
.25x + .55y = .43(100) = 43
SOlving simultaneously, we get:
x = 99.67 kg 25% copper alloy
y = 0.33 kg 55% copper alloy