Answer:
78.7
Step-by-step explanation:
The number has 4 significant figures: 7,8 6 and 5.
To round off to 3 significant figures, the target digit is the third significant figure in the number.The determining digit is the fourth significant figure in the number; it is 5 hence the target digit will go up by 1 and any digits to the right of it will be rounded down to 0.