a) (-3/5 * 0.8 - 13/25) * 0.7 =

1. Convert decimals to fractions: (-3/5 * 4/5 - 13/25) * 7/10.
2. Perform multiplication inside the parentheses: (-12/25 - 13/25) * 7/10.
3. Perform subtraction inside the parentheses: (-25/25) * 7/10 = -1 * 7/10.
4. Perform the final multiplication: -7/10.