[1] n = -2
We will convert the words given into a mathematical equation and then solve by isolating the variable. Let n be "a number"
19 decreased by four times a number is 17
19 - four times a number is 17
19 - 4 n is 17
9 - 4n = 17
-
9 - 4n = 17
- 4n = 8
n = -2
[2] x = -1, y = 3, or (-1, 3)
I will plug the first equation into the second from the system of equations given to us because it already has an isolated variable, y.
2y - 2x = 8
2(2x + 5) - 2x = 8
4x + 10 - 2x = 8
2x = -2
x = -1
Now, I will plug this value back into the equation and solve for y.
y = 2x + 5
y = 2(-1) + 5
y = -2 + 5
y = 3