Please help!
The width of a rectangle is one-fifth of its perimeter. If the length of the rectangle is 15 inches, what is its width in inches?

10 inches

Step-by-step explanation:

w = 1/5 P

Multiply each side by 5

5w = 1/5P *5

5w =P

We know the perimeter of a rectangle

P = 2(l+w)

We can set the two equations equal

5w = 2 (l+w)

l =15 inches

We can substitute 15 in for the length

5w = 2(15+w)

Distribute

5w = 30 +2w

Subtract 2w from each side

5w -2w = 30+2w-2w

3w =30

Divide each side by 3

3w/3 = 30/3

w =10

The width is 10 inches

The formula for perimeter is: P=2W+2L

Rewrite as: 2W  = P-2L

Divide all terms by 2: P/2-L=W

Width is 1/5p, replace W in the equation: P/2-L= 1/5P

Multiply  each term by 10: 5P-10L=2P

Subtract 2p from both sides and add 10L to both sides: 3P=10L

Lenght is given as 15 inches, replace L with 15 and multiply: 3P=150

Divide both sides by 3: P=50

W=1/5P = 10 inches