13a.) If you're dividing and the base (in this case the base is 10) is the same, subtract the exponents.

13b.) If you're multiplying and the base is the same, then you add the exponents:

13c.) This is similar to 13b:
after solving
we get 
Step-by-step explanation:
We need to find the value of x in:

Solving:

So, after solving
we get 
Keywords: Solving the expression
Learn more about Solving the expression at:
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See attached PDF. (The censor thinks there are some unseemly words in there.)
X=7 and y=4 are the correct equations