If the ratio of lengths, radii and Youngs moduli of steel and brass wires in the figure are a, b and c , respectively

Explanation:

Extension of road due to force can be written as 

Δl=FL/AY where F is the force Y is the young modulus A area Y is the young modulus.

Now it can be written 

The ratio of extension of steel and brass 

(Δl_s)/(Δl_b 〖〗=F_s/F_b ×L_s / L_b ×A_b / A_s ×Y_b / Y_s

⇒(Δl_s)/(Δl_b 〖_〗)=3mg/2mg×a×1/b^2 ×1/c

⇒(Δl_s)/(Δl_b 〖_〗)=3a/(2b^2 c)