This is an algabraic problem, so we would use variables:
Length=x
Width=y
The length is four times the width, so
x=4y
Since the equation for perimeter is P= 2(x+y), you would instead substitute 4y for x, and 7 for the perimeter.
7=2(4y+y)
Simplify.
7=2(5y)
7=10y
y=7/10
Since y is 7/10, you would substitute 7/10 into the equation x=4y.
x=4(7/10)
x=14/5
So, the dimensions are 7/10 x 14/5.
Hope this helps!
