Salut! :)
..x kg.....3,2 kg........
2CuO -> 2Cu + O2
160 kg...128 kg......
x = ( 160 kg × 3,2 kg )/128 kg = 4 kg CuO
...y kg.........4 kg............
CuSO4 -> CuO + SO3
.160 kg.....80 kg..........
y = ( 160 kg × 4 kg)/80 kg = 8 kg CuSO4
r = mp/mt × 100
80/100 = mp/8 kg
mp = ( 80 × 8 kg )/100 = 6,4 kg CuSO4