Can someone explain to me how to do this? i’m so confused

I think it’s going to be 7! Because since the other triangle is 1 and 3 it’s just 2 more so I just added to more to 5 getting me 7!! I think lol

Proportion box
3 over 1 is equal to m over 5
So it’s 1m= 15
And then you divide so it’s 1/m=15/1
And it equals to 15

A’b’c’ are the coordinates to the new location of the transformed triangle abc. find the distance between the coordinates points to use for your calculations.