The area of a rectanglular sandbox is (5x + 40) feet. Factor 5x + 40 to find possible dimensions of the sandbox

5x+40 factors to 5 (x+8). Notice how distributing the 5 back through to each term in the parenthesis gives

5 times x = 5x

5 times 8 = 40

So 5 * (x+8) = 5*x+5*8 = 5x+40

Therefore, the factors are 5 and (x+8).

The dimensions of the sandbox are 5 feet by (x+8) feet.

We don't know the numeric value of (x+8) since we don't know the value of x, so we leave it as is.