The sum of three numbers is 57 The second number is 2 times the first.
The third number is 18 less than the second.
What is the third number?

The first number is 15. The 2nd number is 30 cuz it’s double the first. The third number is 18 less than 30 so it is 12. They all add up to 57. Third # = 12

First subtract 10 from both side
y^2+6y-16=0
(y+8)(y-2)=0
-8 and 2