y=-6x+15 and -7x-6y=-3
using substitution, take the y value of -6x+15 and substitute it into the second equation
-7x-6 (-6x+15) =-3
multiply through, combine like terms, and set x on one side of the equation
-7x +36x -90 = -3
29x = 87
x = 87/29 = 3
now substitute the found value for x back into either original equation
y=-6(3)+15
y= -18 +15 = -3