$\left(+\frac{3}{5}\right)+\left(-\frac{7}{5}\right)$

Step 1 ：Given the problem \(\left(+\frac{3}{5}\right)+\left(-\frac{7}{5}\right)\)

Step 2 ：This is a simple addition of two fractions. The fractions already have the same denominator, so we can directly add the numerators. The operation is as follows: \(\left(+\frac{3}{5}\right)+\left(-\frac{7}{5}\right) = \frac{3 - 7}{5}\)

Step 3 ：Calculate the numerator: 3 - 7 = -4

Step 4 ：The denominator remains the same: 5

Step 5 ：Simplify the fraction to get the final result: \(-\frac{4}{5} = -0.8\)

Step 6 ：\(\boxed{-0.8}\) is the final answer