$${\text{Evalute}}:\frac{{{{\left( {2.39} \right)}^2} - {{\left( {1.61} \right)}^2}}}{{2.39 - 1.61}}$$

$$\eqalign{ & \text{Let } a = 2.39 \text{ and } b = 1.61 \cr & {\text{Given Expression}} \cr & = \frac{{{a^2} - {b^2}}}{{a - b}} \cr & = \frac{{\left( {a + b} \right)\left( {a - b} \right)}}{{ {a - b} }} \cr & = {a + b} \cr & = {2.39 + 1.61} \cr & = 4 \cr} $$