1. The problem is to simplify the expression $(-15) \times \left(+ \frac{3}{5}\right)$.\n2. First, multiply the numbers ignoring the sign: $15 \times \frac{3}{5} = \frac{15 \times 3}{5} = \frac{45}{5}$.\n3. Simplify the fraction: $\frac{45}{5} = 9$.\n4. Now, consider the signs: $-15$ is negative, and $+\frac{3}{5}$ is positive, so the product is negative.\n5. Therefore, the final answer is $-9$.