Derek's score on a test was 90 percent. He had 72 questions right. How many problems were on the test?
1 answer:
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Multiply the first equation by 1.5, to get:
Subtract the second equation from this:
Substituting into the first equation:
Therefore, it takes 1/12 minute to print a black-and-white page, and 1/8 minute to print a colored page.
Subtract the second equation from this:
Substituting into the first equation:
Therefore, it takes 1/12 minute to print a black-and-white page, and 1/8 minute to print a colored page.