Question

The sum of two numbers is 60 and the difference is 12. What are the numbers?

Answer 1

let one of the numbers be 'x' and the second number be 'y'

you know that the sum of the two numbers is 60 so you can say
x + y = 60

you know the difference of the two numbers is 12 so:
x - y = 12

now you can solve very simply

Starting with the second equation, if you know x - y = 12, then x has to equal y + 12

so if you know x = y + 12, then go back to the first equation
x+y =60
(y+12)+y=60
2y+12=60
2y = 48
y=24

now go back to your equation for x:
x = y+12

since we now know that y=24,
x=24+12= 36