Question

Simon has a rectangular garden that is ten feet wide. The perimeter is 50 feet. What is the area of her garden?

Answer 1

So the perimeter is the measurement of the shape all around. I marked the perimeter in green. 

Let's use l for the unknown side.

Since the equation to find the perimeter of a rectangle is
(p = perimeter, l = length, w = width)
p = l + l + w + w
Since w = 10, and p = 50..
50 = l + l + 10 + 10
Simplify:
50 = 2l + 20
Now let's solve:
Subtract 20 from each side. 
30 = 2l
Divide by 2 on each side.
15 = l

Now that we know the length is 15, we can use this equation to find the area. 
(a = area)
a = wl
Since w = 10, and l = 15...
a = 10 · 15
Solve:
a = 150

The answer is 150.

Hope this helped! If you have anymore questions or don't understand, please comment on my profile or DM me. :)

Answer 2

Width W = 10, length L = ?
50 = 2L + 2W
2L = 50 - 2*10 => L = 15

area = L*W = 15*10 = 150 sq.ft.