Two numbers have a sum of 18. If the small number doubled, and then subtracted from the larger number, the difference is 9. X represents the smaller number, Y represents the biggest number. Write an equation to model the difference of the numbers.

Question

Two numbers have a sum of 18. If the small number doubled, and then subtracted from  the larger number, the difference is 9. X represents the smaller number, Y represents the biggest number. Write an equation to model the difference of the numbers.

anonymous · Answer

Use the equations $$18 = x +y$$ and $$9 = y - 2x $$