Answer:
1.53 + 2.786 + 3.3 = 7.6
Explanation:
Significant figures is the number of digits that carry precision in a number.
In mathematical operations involving significant figures, an answer is no more precise that the least precise number used to get the answer.
For addition, look at the places to the decimal point. Add in the normal fashion, then round the answer to the least number of places to the decimal point of any number in the problem.
To find the sum of 1.53 + 2.786 + 3.3 you must:

Because 3.3 is the number with the smallest sig figs, the result should have as many decimal places as the number with the smallest sig figs. Therefore, 7.6.