The sides of a rectangle are in a ratio of 3:4 and the area is 300 sq. ft. find the length and width

L = 20 and W = 15
Explanation:
Let's review what is known about the rectangle in question - the area is 300 cm squared and the ratio of the Length to the Width (which I'll shorten to L and W) is 4:3.
Let's start with the ratio. We know that they are related to each other - 4 of a basic unit of length for L and 3 of that same basic unit of length for W. So we can say that
L =
4
x
and W =
3
x
We also know from the formula for the area of a rectangle that LW = Area of the rectangle. Substituting in the terms with the x's in them gives us
(
4
x
)
(
3
x
)
=
300
so let's solve for x:
12
x
2
=
300
x
2
=
300
12
=
25
x
=
√
25
=
5
(ignoring the negative root since that makes no sense in this application)
Substituting x back into our equations for L and W, we get
L =
4
(
5
)
=
20
and W =
3
(
5
)
=
15
Checking our work - there is a ratio of L:W of 4:3. And LW =
20
⋅
15
=
300
Hope this is what you meant