y =x+10
y =6x+30
substitute x+10 into the 2nd equation anywhere you see y
x+10 = 6x+30
subtract x from each side
x-x+10 = 6x-x+30
10 = 5x+30
subtract 30 from each side
10-30=5x+30-30
-20 = 5x
divide by 5 on each side
-20/5 =5x/5
-4=x
now solve for y
y=x+10
y = -4 +10
y=6
Answer: x=-4
y=6
or (-4,6)
3. y = -3x-6
6x+5y=-30
6x+5(-3x-6) =-30
5x-15x-30=-30
-20x-30=-30
-20x=0
x=0
y = -3x-6
y=-6
