So basically all you do is this, on your assignment youll see words and stuff that are in colors. They also give you a formula for that. Its really easy.
So, you have 20000, 5%(0.5), 4 and 2. 20000 is blue, 5%(0.5) is orange, 4 and 2 are purple. So you do 20000 x 0.5 and you get 10000. So now you do 10000 x 4 x 2 and you get 80000xxx(or just 80000).
Or do 10000 x 4. Then after that take the result of 10000 x 4 and do x2. :)
I think I should the work enough, and good luck with the assignment.
Hope I helped-Aced