Solve this numerical..

Dear Student,
Given,
Resistance of a nichrome wire, R = 10 ohm
Let the length l and area of cross-section a of the nichrome wire be L and A respectively.
​​​​​​Then
$$\begin{gathered} R=\rho \frac{L}{A} \\ where, \\ \rho is the resistivity of the nichrome wire \end{gathered}$$

Length of another nichrome wire, L' = 3L
Its area of cross-section, A'=4A
Let the resistance of the another wire be R'. 
Then
$$\begin{gathered} R\text{'}=\rho \frac{L\text{'}}{a\text{'}}=\rho \frac{3L}{4A}=\frac{3}{4}\left(\rho \frac{L}{A}\right)=\frac{3}{4}R \\ Given, \\ R=10 ohm \\ Then, \\ R\text{'}=\frac{3}{4}\times 10=\frac{15}{2}=7.5 ohm \end{gathered}$$
Regards