Math
posted by Elizabeth .
I don't understand this quadratic equation: The ratio of the measures of the length and width of a rectangle is 5:7. the area of the rectangle is 1,715 square feet. Find the dimensions of the rectangle.

length = 7 x
width = 5 x
7x * 5 x = 1715
35 x^2 = 1715
x^2 = 49
x = 7
7 x = 49
5 x = 35