Answer:
458.910
Explanation:
To calculate the sum, we need to add each of the numbers in order
1. 23.456
+ 90.354
_________
113.810
Then we add the next number to the above total, (to understand better, 345.1 is the same as 345.100-This is to make the two numbers have the same decimal places
2. 113.810
+ 345.100
________
458.910