Please help me!
Solve the system of linear equations by substitution
y = 3x - 3

An advertising firm has an old computer that can prepare a whole mailing in 6 hours. with the of newer model the job is complete in 2 hours. how long would it take the newer model to do the job alone?

Xy x xy if a and b are positive integers such that a*b=9 and b*a=72 what is the value of a/b

At a book fair, joe bought 24 books at 3 for $5 and had $2 left. how much money did he have at first?