Answer
See below.
Work Step by Step
We know that by the Slope Formula: if $P_1(x_1,y_1)$ and $P_2(x_2,y_2)$ are on a line, then the slope is: $m=\frac{y_2-y_1}{x_2-x_1}$.
a) Hence here: $m=\frac{-1-3}{5-(-1)}=-2/3.$
b) This means that if $x$ increases by $3$ units, then $y$ decreases by $2$ units.
