Answer:
1, 3
Step-by-step explanation:
1. 2.3 - 2.3 = 0
2. -3.7 + -4.1 = -7.8
3. -2.6 - (-12/4) = 0.4 = 4/10 = 2/5
4. 5/2 + (-2.5) = 0
5. 72- (-100)
72+100 = 172
