7.1. Given a rectangle where the length is three times the width. It is known that the perimeter of the rectangle is numerically equal to its area. Find the sides of the rectangle.
Answer: $\frac{8}{3}$ and 8. Solution. Let $x$ be the width, then $3 x$ is the length of the rectangle. From the conditions of the problem $2(3 x+x)=3 x \cdot x \Leftrightarrow 8 x=3 x^{2}$. From this, dividing by $x(\neq 0)$, we get $x=\frac{8}{3} ; 3 x=8$.