The equations he came up with are:
12x+6y= 120
4x + y = 30

Answer:
x=5, y=10. (5, 10).
Step-by-step explanation:
12x+6y=120
4x+y=30
--------------------
2x+y=20
4x+y=30
-------------
y=20-2x
4x+(20-2x)=30
4x+20-2x=30
2x=30-20
2x=10
x=10/2
x=5
4(5)+y=30
20+y=30
y=30-20
y=10