It takes a printer 21 2 min to print 24 black-and-white pages and 4 color pages. It takes the same printer 31 4 min to print 30 black-and-white pages and 6 color pages. Let b represent the time in minutes needed to print a black-and-white page and c represent the time in minutes needed to print a color page.

Multiply the first equation by 1.5, to get:

(1.5) (24b+4c) + 1.5 (2.5)

36b + 6c + 3.75

Subtract the secound equation from this:

6b + 1/2

b = 1/12

Substituting into the first equation:

24b + 4c + 2.5

24 * (1/12) + 4c + 2.5

2+4 + 2.5

4c+o. 5

c + 1/8

Therefore, it takes 1/12 minute to print a black-and-white page, and 1/8 minute to print a colored page.