Triangles abc and def are similar. what is the length of side ef

To find that out, we must find out how much larger <DEF is than <ABC 
So we take the sides DE and divide it by AB
4.5/3=1.5
That means <DEF is 1.5 times larger than <ABC
So now, we take BC, and multiply it by 1.5
2 x 1.5 = 3
So EF=3
Hope this helps!