All you have to do is subtract the equations to get your solution.
1. -18 1/5 - (-2 3/5) = -15 3/5
2. 49.40 - (-85.63) = 135. 03
3. -52.89 - (-25.63) = -78.52
4. -96 2/9 - 24 4/9 = -120 2/3
Note - when there is follow by a subtraction sign and then parentheses such as the examples of 1,2, and 3 you distribute that subtraction sign over. Which will result in positive number.
So, like - (-85.63), distribute the subtraction sign which will result into a positive 85.63.