Chapter 1 - Introduction to Algebraic Expressions - 1.5 Addition of Real Numbers - 1.5 Exercise Set - Page 42: 53

$-\frac{1}{15}$

To add two numbers with different signs, we subtract their absolute values ($\frac{2}{5} - \frac{1}{3} = \frac{6}{15} - \frac{5}{15} = \frac{1}{15}$) and take the sign of the larger absolute value, which is negative ($-\frac{1}{15}$)