please help thank you so much

Answer:
The common difference is -1.4
Step-by-step explanation:
The common difference is found by taking 2nd term and subtracting the first term
7.3-8.7 = -1.4
Lets check by taking the 3rd term and subtracting the 2nd term
5.9-7.3 = -1.4
The common difference is -1.4