doubt for experts

Question

An alloy is to contain copper and zinc in the ratio 9:4 the zinc required to be melted with 24 kg of copper is
answer
let copper be x kg
9:24=24:x
9x=4*24
x=10.666666
my doubt is zinc required 24 kg of copper
means z=24*c

Answer 1

x = zinc

 

9 / 4 = 24 / x                inverses of equal fractions are equal

4 / 9 = x / 24                multiply both sides by 24

96 / 9 = x

10 2/3 = x