The diagram below shows a sandbox and the frame that
surrounds it. what is the area of the frame (the shaded area)?
(the length and width are in feet)

8x+16  ft^2

Step-by-step explanation:

First we find the total area of the large rectangle

A = l*w

A = (x+3) * (x+5)

FOIL

A = x^2 +5x+3x+15

A = x^2 +8x+15

Now we find the area of the inner rectangle

A = lw

A = (x+1) (x-1)

FOIL

A = x^2 -x+x -1

A = x^2 -1

To find the shaded area, take the large rectangle and subtract the small rectangle

x^2 +8x+15 - (x^2 -1)

Distribute the minus sign

x^2 +8x+15 - x^2 +1

Combine like terms

8x+16

answer: 48

just remember to use pemdas:

parentheses

expressions

multiplication

division

addition

subtraction