In order to find the solution to the given system of equations, proceed as follow:
Replace the first equation into the second equation and solve for y:
-3x - 7y = 18
-3(-2y - 6) - 7y = 18
6y + 18 - 7y = 18
6y - 7y = 18 - 18
-y = 0
y = 0
Next, replace the previous value into the first equation of the system and solve for x:
x = -2y - 6
x = -2(0) - 6
x = -6
Hence, the solution of the system is x = -6 and y = 0