7y + 2x = 84
7y-7y + 2x = 84-7y
2x = 84-7y
2x/2 = 84-7y/2
x=42-3.5y
3y+11x=107
3y+11(42-3.5y)=107
3y+11(42) (11)(-3.5y)=107
3y+462-38.5y=107
462-35.5y=107
462-35.5y-462=107-462
-35.5y=-355
-35.5y/-35.5=-355/-35.5
y=10
x=42-3.5y
x=42-3.5(10)
x=42-35=7