The ratio of the perimeters is 5: 7. Knowing that the ratio of corresponding side lengths is the same as the ratio of the perimeters, we can write a proportion in terms of x. Be sure to keep the larger side length and the larger perimeter on the same side of the fraction bar. Notice that we will write the ratio of the perimeters as a fraction.
12/x=5/7
Let's isolate x and find its value!
