7/9 + 2/3 =

Possibly nothing.

A/b + c/d = (ad + bc)/(bd)

regardless of the similarity of the fractions. If the fractions are similar, b=d and the result simplifies to

a/b + c/b = (a+c)/b

When adding or subtracting similar fractions, you can leave out the step of making the fractions similar before you perform the operation. (They are already similar, so the step is unnecessary.)

A/b + c/d = (ad + bc)/(bd)

regardless of the similarity of the fractions. If the fractions are similar, b=d and the result simplifies to

a/b + c/b = (a+c)/b

When adding or subtracting similar fractions, you can leave out the step of making the fractions similar before you perform the operation. (They are already similar, so the step is unnecessary.)

To add or subtract dissimilar fractions, restate them as equivalents that are similar fractions. Then add or subtract as you would similar fractions. To add or subtract similar fractions, add or subtract the numerators and express the result over the denominator. This is equivalent to factoring out the denominator of each fraction and performing the arithmetic as you normally would.

__Example__2/3 - 1/4 (dissimilar fractions) = 8/12 - 3/12 (restated as similar fraction equivalents) = (1/12)*(8 - 3) (denominator factored out) [you can also write this as (8-3)/12] = (1/12)*(5) (arithmetic done in the normal way) = (1*5)/12 (product computed in the normal way) = 5/12