How do you work this problem out and show it in scientific notation

For the first one, (4.5 * 10^2) - (1.3 * 10^8), if we were to expand that out it would be the same as:

(450) - (130000000)
Although this can be done by inputting into the calculator, it's all just a matter of moving the decimal
With  (4.5 * 10^2), we know that 10^2 is the same as 10*10 = 100
so (4.5 * 10^2) is basically (4.5 * 100) = 450 (or moving decimal point to the right twice)

To make it easier, just put (4.5 * 10^2) into a calculator and that gives an answer of -129999550. 
To show this in scientific notation, it must have some form of 10 to the power of an exponent.
Letting the variable be y here...
We know your questions are in the form of y.y x 10^y and so the answer must be in the same form. 
Here for -129999550, the decimal can be moved back (to the left) 8 spots or times to leave the answer in the form of y.y 
Thus, let -129999550/10^8 = -1.2999955 
The final answer in scientific form would be -1.2999955 * 10^8

For the second question, we use the same steps. 
(9.3 * 10^3) - (1.3 * 10^5)
= (9.3 * 1000) - (1.3 * 100000)
= (9300) - (130000)
= -120700 (decimal point can be moved back 5 spots or times to leave answer in form of y.y)

-120700/10^5
= -1.207
Therefore the answer is -1.207 * 10^5