If a + b = 2c, find aa - c + cb - c = ?

Answer: Option B

$$\begin{array}{rl}& a+b=2c\\ & \text{Taking }a=2,b=4\text{ and }c=3\\ & \text{So,}2+4=2\times 3\\ & \boxed{6=6}\\ & \text{Now,}\frac{a}{a-c}+\frac{c}{b-c}\\ & =\frac{2}{2-3}+\frac{3}{4-3}\\ & =\frac{2}{-1}+\frac{3}{1}\\ & =1\end{array}$$