The Sum Of Two Numbers Is 21 And Their Difference Is 1

The problem given says that 2 unknown numbers are given, whose sum is equal to 21 and the difference is 1. Let's find the two numbers :

When we add the two numbers :
X + Y = 21

The difference of two numbers :
X - Y = 1

Solution :

If we add the two equations eachother , then we can find the first number.

X + Y = 21
X - Y = 1

2X = 22

Let's divide 22 to 2 for the first number "X" .

X/2 = 11

First number is 11

X + Y = 21
So ;
11 + Y = 21
Y = 21 - 11
Y = 10

Second number is 10

Question & Answer
The Sum Of Two Numbers Is 21 And Their Difference Is 1 : 11 And 10