Step-by-step explanation:
If x is the mass of 30% copper alloy, and y is the mass of 65% copper alloy, then:
x + y = 80
0.30x + 0.65y = 0.51(80)
Solving the system of equations using substitution:
0.30x + 0.65(80 − x) = 0.51(80)
0.30x + 52 − 0.65x = 40.8
11.2 = 0.35x
x = 32
y = 80 − x
y = 48
The metalworker needs 32 kg of 30% copper alloy and 48 kg of 65% copper alloy.
