Question

two cartons of milk and one sandwich cost 3$ and one carton of milk and two sandwiches cost 4.20$. whats the cost of one carton of milk

Answer 1

2m+s=3
m+2s=4.2

Then you would solve using substitution or combining the equations, etc

Answer 2

my calculator has an option that solves two line equations.

Answer 3

Using substitution you get: s = 3-2m
m + 2(3-2m) = 4.2
m+6-4m=4.2
-3m=-1.8
m=0.60
had a typo earlier