A lawn mowing service charges a 7 per hour. Write an equation for the cost of a job as a function of the hours it takes. If a particular lawn costs $38 to mow, how many hours did it take?
One number is twice as large as three more than another number. The product of the numbers is 20. What are they?
Substitute eq 1. into eq 2.
Substitute back into eq 2.
Two solutions: