Hello Math Help.

as the title says, i need help with some problems. Math has never been my strong suit, i have a test Monday and I'd like to figure out how to solve these problems thanks for your help.

for the first one answer i got 6 and my calculator gets 57

Operation with integers

1 54-6÷2+6=?

my work

54-6÷2+6

48÷2+6

48÷8

6 what am i doing wrong?

Operation with fractions

3 if (3/4-2/3)+(1/2+1/3) is calculated and the answer reduced to simplest term, what is the denominator of the resulting fraction?

my work3/4

4 1/2(2/3÷3/4)-(4/5x5/6)=?

exponents

8 saying 4 < öx < 9 is equivalent to saying what about x?

ratios and proportions

10 if the total cost of x appes is b cents, what is a general formula for the cost, in cents, of y apples?

12) 12) This year. 75% of the graduating class of harriet tubman high school had taken at least 8 math courses. of the remaining class members, 60% had taken 6 or 7 math courses. what percent of the graduating class had taken fewer then 6 math courses

please show work so i can understand and thank you for your help.