Question

the height of a right square pyramid that has a rectangular base area of 70 units and a volume of 140 cubic units

Answer 1

well, the pyramid is a square pyramid, so, the "rectangle" at the bottom, is really a square, well, a square is a rectangle as much as it's a quadrilateral
like the one in the picture below

now
`\bf \textit{volume of a pyramid}\\\\ V=\cfrac{1}{3}Bh\qquad \begin{cases} B=\textit{base area}\\ h=height\\ -------\\ B=70\\ V=140 \end{cases}\implies 140=\cfrac{1}{3}\cdot 70h`

solve for "h"