Question

What are the steps for adding and subtracting mixed numbers with unlike denominators

Answer 1

Well, there are different ways to do this if you are really familiar with fractions, but "officially" :P

1) convert mixed numbers to improper fractions.

rule:  a b/c = (ac+b)/c

2)  make all fractions have a common denominator...

a/b+c/d

(a/b)(d/d)+(c/d)(b/b)

(ad/bd)+(cb/bd)

3)

The simplify your final answer with greatest common denominator or convert back to mixed number if needed...

Answer 2

Say we have 2/3 and 1/2.

Multiply 2/3 to make 4/6.

Multiply 1/2 to make 3/6.

Suddenly, you can do whatever you want with the problem because you are working with common denominators.

I hope that this helps.  If you get stuck on future problems, just find the thing that the two denominators have in common after multiplying them a few times.  An example would be 4 and 7.  The lowest number that they can multiply to that they have least in common is 28.