Question

The sum of two numbers is 56,and their difference is 10.What are the numbers?

Answer 1

So, X + Y = 56, and X - Y = 10.
We can say X = Y +10, so we can also say:
(Y+10) + Y = 56 
2Y + 10 = 56

2Y = 46

Y = 23.

Then we can say 

X - 23 = 10

So X = 33