The sum of two numbers is -1. when twice the first number and four times the second number are added, it equals -10. what are the two numbers?

Let the two number be x and y.
x+y=-1i
2x+4y=-10ii
solving the simultaneous equation we have:
from equation i, making x the subject we get:
x=-1-yiii
substituting iii in ii we get:
2(-1-y)+4y=-10
-2-2y+4y=-10
2y=-10+2
2y=-8
y=-8/2=-4
substituting the value of y in iii we get:
x=-1-(-4)
x=-1+4
x=3
therefore the first number is 3 and the second number is -4

Where are the functions?