How to find slope, when two function points is given?

Find the slope of the function, when points $A(1,3)$ and $B(7,12)$ belongs to this function?

If we have two points of the straight line function, we can use this formula $\frac{y_2-y_1}{x_2-x_1}$ to find the slope of this line. So there we have:

$$\text{Slope}=\frac{y_2-y_1}{x_2-x_1}=\frac{12-3}{7-1}=\frac{9}{8}=1\frac{1}{8}$$