$$\left( {\frac{{1.49 \times 14.9 - 0.51 \times 5.1}}{{14.9 - 5.1}}} \right)$$     is equal to :

$$\eqalign{ & \left( {\frac{{1.49 \times 1.49 \times 10 - 0.51 \times 0.51 \times 10}}{{1.49 \times 10 - 0.51 \times 10}}} \right) \cr & = \frac{{10\left[ {{{\left( {1.49} \right)}^2} - {{\left( {0.51} \right)}^2}} \right]}}{{10\left( {1.49 - 0.51} \right)}} \cr & = \left( {1.49 + 0.51} \right) \cr & = 2 \cr} $$