Four pens cost $2 less than two markers. Three pens and nine markers cost $54. Find the cost of each.

Answer 1

4 p = 2 m -2 so m = 2 p + 1

3 p + 9 m = 54
3 p + 9 (2 p + 1) = 54 etc

Answer 2

4p - 2m = 2 ---> 2p - m = 1 or m = 2p-1

3p + 9m = 54

sub in
m=2p-1 into the other equation and solve