Addition and Subtraction of fractions

When adding or subtracting fractions, the denominators must be the same

Example:

$$\begin{array}{rl}& \text{Evaluate}1\frac{1}{2}+2\frac{3}{5}-\frac{4}{7}\\ \\ & 1+\frac{1}{2}+2+\frac{3}{5}-\frac{4}{7}\\ \\ & 3+(\frac{1}{2}+\frac{3}{5}-\frac{4}{7})\text{Change the fractions so they have the same denominator}\\ \\ & 3+(\frac{1\times 35}{2\times 35}+\frac{3\times 14}{5\times 14}-\frac{4\times 10}{7\times 10})\text{The LCM of 2, 5, and 7 is 70}\\ \\ & 3+(\frac{35}{70}+\frac{42}{70}-\frac{40}{70})\\ \\ & 3+\frac{35+42-40}{70}\\ \\ & 3+\frac{37}{70}\\ \\ & 3\frac{37}{70}\end{array}$$