$\begin{align}  & A\left( 3,\text{ }12 \right)\text{ },\text{ }B\left( 5,\text{ }22 \right) \\ & \text{Using two points form, the equation of the line} \\ & \frac{y-{{y}_{1}}}{x-{{x}_{1}}}=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}} \\ & \frac{y-12}{x-3}=\frac{22-12}{5-3} \\ & \frac{y-12}{x-3}=5 \\ & y-12=5(x-3) \\ & y-12=5x-15 \\ & y=5x-3 \\\end{align}$