Kevin brought 2 pens and 2 erasers for $1.50. Lynn brought 1 pen and 1 notebook for $1.50. Maria brought 2 notebooks for $2.20. How much did Neal pay for 4 erasers?
2p + 2e = 150 -----> p + e = 75
p + n = 150
2n = 220
from last equation, solve for n
sub that into the second equation to find p
sub that into the first equation to find e and the mystery is solved.