Question

A certain drug is made from only two ingredients: compound A and compound B. There are 7 millimeters of compound A used for every 5 millimeters of compound B. If a chemist wants to make 900 millimeters of the drug, how many millimeters of compound A are needed?

Answer 1

Answer: The answer is: 525 millimeters of compound A are needed.

Explanation:
You have to put it in equation form to solve for compound A. To do this use variables.

7(x) + 5(x) = 900
12(x) = 900
x = 900/12
x = 75
When we get 75 you have to plug it into compound A to get this:
7(75) = 525

To confirm our answer we plug in 75 to both variables.
7(75) + 5(75) = 900

I hope this was able to help you :D