The numbers in this addition problem are given in scientific notation. First we should convert these values into decimal notation by moving the decimal points over by the power of 10 that the significant figures are being multiplied by.
The first number is being multiplied by 10^3, so the decimal place will move to the right 3 places to become 1240.
The second number is being multiplied by 10^4, so it becomes 23000.
Add these together to get:
1240 + 23000 = 24240
The answer is 24240.