You start off by multiplying the second bracket by -1 to get rid of the bracket.
So,
(2x3 + x2 - 4x) - 9x3 + 3x2 =
2x3 +x2 - 4x - 9x3 + 3x2 =
(2x3 - 9x3) + (x2 + 3x2) - 4x =
-7x3 + 4x2 - 4x
500 in 2:3 is saying that there are five different parts (2 + 3)
This means that 500 needs to be split into five, which is 100.
After that all you need to do is put 2 'sections' on one side and 3 on the other.
For example, 2 : 3 = 2( x 100) : 3( x 100)
= 200 : 300
32/1x5/6=160/6
6 goes into 160 26 times, with an extra 4.
Your answer is 26 4/6, or 26 2/3.
Hope this helps :-)