Hey There :)
We can solve by 2 ways ( The 2nd way might be easier )
→ To make 1 brass alloy, the ratio of copper to zinc is 3 : 2
Brass = copper + zinc
= 3 : 2
3x : 2x
Copper needed is 120g
↓
3x = 120g
Divide by 3 to isolate x
x = 40
Ratio of Zinc is 2
substitute 40 in place of x
2x = 2 ( 40 ) = 80g
Or
→ 3 : 2
120 : p
Cross multiply
3p = 120 x 2
3p = 240
p = 80g
80g of Zinc will be needed with 120g of Copper
We can solve by 2 ways ( The 2nd way might be easier )
→ To make 1 brass alloy, the ratio of copper to zinc is 3 : 2
Brass = copper + zinc
= 3 : 2
3x : 2x
Copper needed is 120g
↓
3x = 120g
Divide by 3 to isolate x
x = 40
Ratio of Zinc is 2
substitute 40 in place of x
2x = 2 ( 40 ) = 80g
Or
→ 3 : 2
120 : p
Cross multiply
3p = 120 x 2
3p = 240
p = 80g
80g of Zinc will be needed with 120g of Copper