Question

What MUST be true when adding and subtracting numbers in scientific notation?

Answer 1

To be added or subtracted, two numbers in scientific notation must be manipulated so that their bases have the same exponent--this will ensure that corresponding digits in their coefficients have the same place value.

Answer 2

This might help you with your question 2 numbers inside of scientific notation have to be manipulated in order for their own foundations to have the same exact exponent