It’s a trick question, because there are no three numbers that add up to 12.
The answer is 10 + 2 = 12
If you’re having trouble seeing why this is true, try plugging in some other numbers for X and Y. For example, what if X = 3, Y = 9? Then (X + Y) + (X – Y) = 19 – 1 = 18. The problem is that when you subtract 1 from both sides of the equation, it doesn’t change anything: (X + Y) + (X – Y) = 1 + 1, or 2. So we can see that all values of X and Y will result in the same sum.
Last modified: August 16, 2022