How do we do compositions of transformations? 3/7/13

Compositions of transformations, is the result of a second or more transformations performed on the image of the first transformation. It's important and necessary to always do the 2nd transformation first and then the first second.

For example:

1) What is the image of (-4,2) after R90 D3?

So first you the second transformation which is dilating (-4,2) by 3. All you do is multiply 3 by -4 & 2. Giving you : (-12, 6) 

Then having (-12,6) you do the first composition, which is Rotating it by 90
R90 -> (-y,x) 

So (-12,6) is (-6, 12) 
Answer: (-6,12) 

Question: What is the image(-12,6) after T(5,1) , R180?