"Rules" for manipulating addition and subtraction number sentences to solve for the variable

If your variable is in an addition number sentence:

Addend1 + Addend2 = Sum (original problem format)
Addend2 + Addend1 = Sum
Sum - Addend1 = Addend2
Sum - Addend2 = Addend1

If your variable is in a subtraction number sentence:

Minuend - Subtrahend = Difference (original problem format)
Minuend - Difference = Subtrahend
Subtrahend + Difference = Minuend
Difference + Subtrahend = Minuend

Example:

1/3 - B = 5/24

let's label each piece....

1/3 (min.) - B (sub.) = 5/24 (diff.)

so, we want to solve for our variable, B. In other works, we want to "isolate" our variable all by itself after the equal sign! So, our subtrahend (which is what the variable B is in our original problem) will follow the equal sign if we subtract our difference form our minuend!

1/3 - 5/24 = B

Now find common denominators and solve!!!

1/3 = 8/24 so 8/24 - 5/24 = 3/24 so B=3/24