p=value of a pencil
r=value of a ruler
e=value of an eraser
6p=2r
r=2e
alrigty
we can divide the fist one by 2
3p=r
so
3p=r=2e
neato
12 pencils is equal to ? erasers
3p=2e
times both sides by 4
12p=8e
8 erasers
2 erasers are equal to ? pencils
3p=2e
3 pencils
1 ruler and 4 erasers are equal to ? pencils
3p=r=2e
r+4e=3p+2(2e)=3p+2(3p)=3p+6p=9p
9 pencils
Twelve pencils are equal in value to eight erasers
Two erasers are equal in value to three pencils
One ruler and four erasers are equal the value of nine pencils