Step-by-step explanation:
I first take back the numbers to their original forms that is to say (5.55×10^15) = 5550000000000000 and (8.88×10^18) = 8880000000000000000 therefore the difference of the two will be 887445 which is notated to (8.87445×10^5)
Answer: (8.87445×10^5)