ALGEBRA QUESTIONS!!! (Please help?!)

1) If 15% of x is 42, what is x?

 

2)I need to make $500 per week after tax in order to pay all my bills. The income tax is 20%. What is the smallest pre-tax weekly salary I can earn and still be able to pay my bills after I pay my income tax?
 

3)After my salary was increased by 12%, it was 62,720. What was my salary before the increase?

 

4)After some bad news (due to a revolutionary but ultimately doomed process for making toast in a microwave oven), stock in Seraj Food Industries fell by 40%, to $324 a share. What was the original price of a share?
 

5)Three generations of the Wen family are going to the movies, two from each generation. The two members of the youngest generation receive a 50% discount as children. The two members of the oldest generation receive a 25% discount as senior citizens. The two members of the middle generation receive no discount. Grandfather Wen, whose senior ticket costs $6.00, is paying for everyone. How many dollars must he pay?

 

6)The city imposed a 0.08% tax on the value of dinosaur collections. Sheila had to pay $12 in dinosaur tax. How much is her dinosaur collection worth?

 

7)A city has an assessed valuation of $8,000,000. The rate for school taxes is 60 cents per $100 valuation. If all but 4% of the school taxes were collected, how many dollars were still owed?

 

8)On Tuesday, a radio store reduces all of its prices by 20% from what they were on Monday.

On Wednesday, the store again reduces all of its prices by some percentage from what they were on Tuesday. If the resulting price of a radio is half of the original Monday price, then by what percentage did the store reduce its prices from Tuesday to Wednesday?

 

9)Winston grows green dragon apples. This year, he shipped 80%of these apples to sell at supermarkets and kept the rest to make cider. Of all the green dragon apples he sold to the supermarkets, only 60% of them were bought. If a total of 420 green dragon apples were bought, how many green dragon apples did Winston keep to make cider?

 

10)At a party at the middle school over on third avenue next to the bank, 60% of the students are girls. After these students are joined by 20 more boy students, all of whom like to dance, the party is now 58% girls. How many students are now at the party?

 

11)Ms. Forsythe gave the same algebra test to her three classes. The first class averaged 80%, the second class averaged 85%, and the third 89%. Together, the first two classes averaged 83%, and the second and third classes together averaged 87%. What was the average for all three classes combined? Express your answer to the nearest hundredth.