# Add & subtract rational expressions: unlike denominators

Add and subtract rational expressions with relatively prime denominators by manipulating them to have the same denominators.

### Problem

Tom and Li-Min were each asked to perform the following operation:
start fraction, 7, m, minus, 4, divided by, m, plus, 9, end fraction, plus, start fraction, 8, divided by, 7, m, start superscript, 5, end superscript, end fraction