How do i solve system of equations by substitution
3x-7y=41
x=-2y-21

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).