Question

a mixture contains iron and copper in the ratio of 7:12 . when 30 kg of ron and

Answer 1

Question is incomplete. Correct question will be, 
A mixture contains iron and copper in the ratio of 7:12 . When the mass of the Tron is 30 kg then find the mass of the Copper. 

Solutions ⇒
Let the mass of the iron and copper be 7x and 12x respectively. 

∴ 7x = 30 kg.
∴ x = 30/7 kg.
⇒ x = 4.29 kg.

Also, Mass of the copper = 12x 
 = 12 × (30/7)
 = 51.43 kg. 



Hope it helps.

Answer 2

"Let the mass of the iron would be 7x and

The mass of the copper be 12x respectively.

Therefore, it is given that mass of iron is 30Kg

Then if, 7x = 30 kg.

$x = 30/7 \quad kg$.

Hence, x = 4.29 kg.

Also, Mass of the copper = 12x

(By substituting the value of x) we get,

$= 12\times(30/7)$

The mass of the copper as 51.43 kg. "