Answer:
Step-by-step explanation:
x+2y=10
6y=-3x+30
~~~~~~~~~~~~~~~~
x =10 -2y
substitution
6y=-3x+30
6y=-3(10 -2y)+30
6y = -30 + 6y + 30
6y = 6y
everything disappears.... that means the lines are "the same line"
"co-incident" ... "infinite solutions"
Note" if you ended up with something like 3=0 then the lines are parallel
