Step 1 :We are given that $P S = 7$, $P R = -24-7 x$, and $S R = -13-4 x$.
Step 2 :We know that $P S = P R + R S$.
Step 3 :Substituting the given values into the equation, we get $7 = -24-7 x + -13-4 x$.
Step 4 :Solving this equation, we find that $x = -4$.
Step 5 :Substituting $x = -4$ into the equation for $P R$, we get $P R = -24-7(-4)$.
Step 6 :Simplifying this, we find that $P R = 4$.