So as I was doing me hw, I ran into this question, and I cant figure it out... Anyone wanna try? 7. The ratio of the perimeters of two triangles is 2:5. The perimeter of the larger triangle is 20 cm. What is the perimeter of the smaller triangle?

small/large = 2/5

small/20 = 2/5
cross-multiply
5small = 40
small = 8

check:
8:20
= 4:5