Question

The sum of two numbers is 51 and the difference is 9. What are the numbers?

Answer 1

we dont know what is the two numbers so let us assume that one is x and other is y

so the sum of two numbers will be x+y which is equal to 51

$x+y=51$

and their difference is 9

$x-y=9$

so now we have two equations we can solve this by elimination method.

$x+y=51 x-y=9$

we know that we have -y and +y which is same value with opposite sign so we can cancel it and x+x will be 2x and 51+9=60

$2x=60 x=30$

we can plug x=30 in any one of the equations

$x+y=51 30+y=51 y=21$

$x=30, y=21$

Answer 2

The numbers are 21 and 30