Okay, I just need help understanding and getting the answers for a few questions.

1) A woman's dress originally selling for $50.00 was marked down to yield 20% on cost. If the original profit was 33 1/3% on cost, what will be the new sales price.

2) Find the compound interest on $1000 for 9 months at 8% per annum, interest being calculated quarterly.

[And then I have the expand crap... I seriously don't understand this guys :( Please pity me and help me out :)]

You have to expand each of the following

3) a. (Y+3)(Y+4)

b. (2x-4)(x+8)

c. (7x-4)(3x-9)

d. (x-3)(x+3)

e. (x+3)(y-9)

4) Mr. Drake sold two books at $1.20 each. Based on the cost, the profit on one was 20% and the loss on th e other was 20% On the sale of the books, did he break even? Gain? Lost? Show how much he gained or lost.

5) There are 1600 pupils in a school. 3/8 of them are girls. 43% of the boys and 1/4 of the girls wear glasses. How many students in this school wear glasses?

6) If 12(exponent)x-4=1, What is the value of 3(exponent)x

7) If x is 3% of y and y is 7% of w, find x in terms of w.

Thanks!!!!!

Guys, I know this is alot :( Sorry, but mid-terms are really hard and I really need to understand this stuff :P Kindly try and answer as many questions as possible by tommorow =)