How do you figure out the answer?

-- To add or subtract numbers in scientific notation (like these),
the powers of 10 have to be the same.

In the first problem, you'll need to change one or both factors
to the same power of 10 before you can add them.

         1.3 x 10³ = 13 x 10²  or  1,300
        
         2 x 10²  =  0.2 x 10³  or  200

Change one or both of them so their powers of 10 are the same.
Then addum up.


In the second problem, both factors already have the same
power of 10, so you can go ahead and subtractum.


The third problem is a multiplication.
For multiplication, the factors DON't need the same power of 10.
Just go ahead and multiplyum.
To do that ...

     --  Multiply the mantissas  (the  1.5  and the  2.2)

     --  Add the powers of 10  (the  2  and the  -5)