Question

Use addition or substitution to solve this problem.
To paint his house, Samuel bought 2 cans of paint and one roller for $30. When friends came over to help, he went back to the store and bought three more cans of paint and two more rollers for $50. How much did he pay for a roller?

Answer 1

Our friend Sam goes to the store twice, and buys varying quantities of paint and rollers. The prices of the paint and of the rollers does not change.

We need to set up a linear equation in p (price of one can of paint) and r( price of one roller) for each visit to the store.

First visit: Samuel bought 2 cans of paint and one roller for $30:
2p + 1r = $30

Second visit: He went back to the store and bought three more cans of paint and two more rollers for $50. Write the appropriate equation, below.


Now you have a system of linear equations, and your primary task is to find the price of one roller, which is the value of r. In this problem, we don't bother finding the cost of a can of paint.

How would you go ab out solving this system of linear equation for r?