Given the information on the problem, we can draw the following right triangle:
we can find how high the ladder reach using the pythagorean theorem:
[tex]\begin{gathered} (35)^2=(28)^2+h^2 \\ \Rightarrow h^2=(35)^2-(28)^2=1225-784=441 \\ \Rightarrow h=\sqrt[]{441}=21 \\ h=21ft \end{gathered}[/tex]therefore, the ladder reaches 21 ft high up on the wall
