Question

Ron bought 8 pencils and 2 erasers for $1.66. Sarah bought 12 pencils and 5 erasers for $3.19. What is the cost for 1 pencil and 1 eraser?

Answer 1

p=price of 1 pencil
e=price of 1 eraser

1.66=8p+2e
divide by 2 for simplification
0.83=4p+e

3.19=12p+5e

0.83=4p+e
multiply by -5 and add to obht eration

-4.15=-20p-5e
3.19=12p+5e +
-0.96=-8p

divide by -8
0.12=p
sub back

0.83=4p+e
0.83=4(0.12)+e
0.83=0.48+e
minus 0.48 both sides
0.35=e

1e+1p=0.12+0.35=0.47

cosst is $0.47