Question

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

c=cost of 1 can of paint
r=cost of 1 roller

2c+1r=30

3c+2r=50

so

multiply first equation by -2 and add to 2nd

-4c-2r=-60
3c+2r=50 +
-1c+0r=-10

-c=-10
c=10

sub back

2c+r=30
2(10)+r=30
20+r=30
r=10

payed $10 for a roller