The length of a rectangular portrait is 1.5 times the width. The perimeter is 10 feet.

What is the length of the portrait?

In order to solve the problem above, represent the width by x. With this, the length of the rectangular portrait is 1.5x. The perimeter of the rectangle is two times the sum of the length and width. This translates to,

2 (1.5x + x) = 10 ft, x = 2 ft.

Thus, the length of the rectangular portrait is 3 ft.