select all the pairs of numbers that have the same greatest common factor 16 and 30, 26 and 28, 12 and 28, 22 and 34, 24 and 32

Kylie explained that (-4x+9)^2 will result in a difference of squares because (-4x+9)^2 (-4x+9)^2 =(-4x)^2+(9)^2=16x^2+81

!! 10 ! a westbound jet leaves central airport traveling 635 miles per hour. at the same time, an eastbound plane departs at 325 miles per hour. in how many hours will the planes be 1900 miles apart?

We just started the introduction into circles and i have no idea how to do this.