Answer:
54.62
Explanation:
When you are adding numbers the significant figures for the result must be the smallest number of significant figures from the numbers you are adding.
In this case, you have 8.647 with 4 significant figures
And 45.969 with 5 significant figures
So, your result must have 4 significant figures.
Now, when you add the numbers you obtain:
8.647+45.969 = 54.616
But this result has 5 significant figures, so you need to round to the next integer, in this case, you should round to the number 2 because the number to follow the 1 is greater than 5.
Then you have that 54.616 rounded to the next integer is 54.62 with 4 significatn figures.