What must be added to each term of the ratio 7 : 11, So as to make it equal to 3 : 4?

Answer: Option D

$$\begin{array}{rl}& \text{Let }x\text{ be added to each term}.\\ & \text{According to question},\\ & \frac{7+x}{11+x}=\frac{3}{4}\\ & Or,33+3x=28+4x\\ & Or,x=5\end{array}$$