Me on this
question:
yolanda has finished 45% of the homework problems she was assigned. so far she has finished 27 problems.
a. write 45% as a rate per 100 and then reduce the fraction to lowest terms.
b. how many problems was yolanda assigned? justify your answer.
c. how many problems does yolanda still have to do? show your work.
write the answer in your own words

A. 45/100 reduced = 9/20
(divided 45 and 100 by 5 to get 9 and 20)

B. she has finished 27 problems, which is 45% of her homework. In other words
45% of the total problems = 27 
if we use X to represent the total amount of problems, then: 
45% X = 27
we solved in part A for 45%, which is 9/20, so then:
9/20 x = 27 
now all that's left is to solve for x
first multiply both sides by 20
9x = 540
now divide both sides by 9
x = 60
the total amount of problems, or the number of problems she was assigned is 60 problems. 

C. If the total amount of problems she had to do was 60, and she has already done 27, then 
60 - 27 = the amount of problems she has left
33 = the amount of problems she has left

she has 33 problems left to do.