Question 246
The sum of two numbers can be expressed algebraicly as the sum of two variables:

x + y = 64 (equation #1)

The difference of the same two numbers is expressed in like fashion:

x - y = 42  (equation #2)

We can solve this by substitution by solving the first equation for x;

x + y = 64
--> x + y - y = 64 - y
--> x = 64 - y

We then replace the x in the second equation with (64-y):
x - y = 42
--> (64 - y) - y = 42
--> 64 -y - y = 42
--> 64 -2y = 42

We then add 2y to both sides:

--> 64 -2y + 2y = 42 + 2y
--> 64 = 42 + 2y

Then we subtract 42 from both sides:
--> 64 - 42 = 42 + 2y -42
--> 22 = 2y

Divide both sides by 2:
--> 22/2 = 2y/2
--> 11 = y

Then we go back and replace y in the first equation with 11:
x + y = 64
--> x + 11 = 64

Subtract 11 from both sides of the equation:

x + 11 -11 = 64 -11
--> x = 53

ANSWER: the two numbers are 53 and 11