The paper is 7 cm by (x + 8) cm.
A photo is 5 cm by (x + 6) cm, and is printed in the middle of the paper.
The area of the border/space around the photo is 50 cm².
To find the area of the border around the photo, you find the area of the paper and subtract it by the area of the photo.
The area of the paper:
A = 7 · (x + 8)
The area of the photo:
A = 5 · (x + 6)
Your equation to find the area of the border around the photo is:
(7 · (x + 8)) - (5 · (x + 6)) = A
[area of paper - area of photo = area of border]
Since you know the area of the border, you can plug it in:
(7 · (x + 8)) - (5 · (x + 6)) = 50
Multiply the 7 into (x + 8), and multiply the 5 into (x + 6)
(7x + 56) - (5x + 30) = 50
Distribute/multiply the - to (5x + 30)
7x + 56 - 5x - 30 = 50
Combine like terms
2x + 26 = 50
Subtract 26 on both sides
2x = 24
Divide 2 on both sides
x = 12
