The difference of two numbers is 40. Their sum is 66. Find the numbers.

Let the 2 numbers be a and b. Let a be the larger.

i) "The difference of two numbers is 40" means: a-b=40, thus

a=b+40

ii) "their sum is 66" means : a+b=66

In i) we found that a=b+40, so substitute a=b+40 in ii):

a+b=66

(b+40) + b=66

2b+40=66

2b=26

b=13

a=b+40=13+40=53

the numbers are 53 and 13