Two electric dipoles of dipole moments 1 . 2 × 10 - 30   cm and 2 . 4 × 10 - 30   cm are…

Maximum torque experienced by an electric dipole is ${\tau }_{max}=PE\sin 90°$.

So, ${\left|\tau \right|}_{\max }=PE$

The ratio is $\frac{{\tau }_1}{{\tau }_2}=\frac{P_1{E}_1}{P_2{E}_2}=\frac{1.2\times {10}^{-30}\times 5\times {10}^4}{2·4\times {10}^{-30}\times 15\times {10}^4}=\frac{1}{6}$
 

Hence, the value of $x=6$.