Elliot is building a sandbox in the shape of a triangle. A model of the sandbox is shown. Which expression represents the perimeter of Elliot's sandbox?

Answer 1

To find the perimeter of the sandbox, we need to add up the lengths of all three sides of the triangle.

The top side of the triangle is 7 feet long.
The left side of the triangle is 12 feet long.
The right side of the triangle is 12 feet long.

We can add up these three side lengths to find the total perimeter:

$7+12+12=31$.

So the expression that represents the perimeter of Elliot's sandbox is $\boxed{31}$.