7.55 + 17.002 = 24.552
Significant figures in addition and subtraction: significant figures are considered to be the figures of the entire integer part of the result of the operation, plus the figures of its decimal part that do not exceed the smallest number of decimal places in the quantities involved in the operation.
According to that
The number 24.552, must have 2 decimal places.
So,
Answer: 24.55