The line through A(1, 2) and B(3, k) is parallel to the line through C(0, -1) and D(4, 3)…

Step 1. The slope of $CD$. $\dfrac{3 - (-1)}{4 - 0} = 1$.

Step 2. Parallel. $\dfrac{k - 2}{3 - 1} = 1$, so $k = 4$.

Step 3. Perpendicular. The slope of $AE$ must be $-1$: $\dfrac{5 - 2}{h - 1} = -1$, so $h - 1 = -3$ and $h = -2$.