Question

The sum of two numbers is 21. Their difference is 7. What are the numbers?

Answer 1

The numbers are

14

and

7

.

Step-by-step explanation:

Let the numbers be

x

and

y

.

x

+

y

=

21

x

−

y

=

7

y

=

21

−

x

x

−

(

21

−

x

)

=

7

x

−

21

+

x

=

7

2

x

=

28

x

=

14

∴

14

+

y

=

21

y

=

7

Answer 2

Answer: The required numbers are 14 and 7.

Step-by-step explanation: Given that the sum of two numbers is 21 and their difference is 7.

We are to find the numbers.

Let x and y represents the two numbers.

Then, according to the given information, we have

`x+y=21~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(i)\\\\x-y=7~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(ii)`

Adding equations (i) and (ii), we get

`(x+y)+(x-y)=21+7\\\\\Rightarrow 2x=28\\\\\Rightarrow x=(28)/(2)\\\\\Rightarrow x=14.`

From equation (i), we get

`x+y=21\\\\\Rightarrow 14+y=21\\\\\Rightarrow y=21-14\\\\\Rightarrow y=7.`

Thus, the required numbers are 14 and 7.