What two numbers when added together equal 645 and when subtracted equal 151?

Answer 1

796

Answer 2

You essentially have two equations that you must solve:

x + y = 645

and

x - y = 151

The problem is that you have two variables and therefore it seems impossible to solve, however, the two variables are related to each other. For instance, solving the first equation for y gives you:

y = 645 - x

That is how y relates to x. So, substituting this new value for y in the next equation gives you:

x - (645 - x) = 151

Distribute the negative (remove the parentheses):

x - 645 + x = 151
2x - 645 = 151
2x = 151 + 645
2x = 796
x = 398

Now, plug this new value for x into the first equation:

398 + y = 645
y = 645 - 398
y = 247

Now test:

398 + 247 = 645
398 - 247 = 151

There you have it.