Going off the value of x in terms of y given in the second equation, we can substitute the x in the first equation with the value -2y - 21 to give us the equation
3(-2y - 21) - 7y = 41
Distributing the 3 to the -2y and -12:
-6y - 63 -7y = 41
Combining like terms:
-13y - 63 = 41
Adding 63 to either side:
-13y = 104
And dividing both sides by -13:
y = -8
We can plug in this solution for y to the second equation to obtain a solution for x:
x = -2(-8) - 21
x = 16 - 21
x = -5
So our solution is the pair (-5, -8).
