Instead of doing yours for you, I'll do one exactly step by step
like yours.



Make sure that every letter has an exponent. The m in the parentheses
on the left is not showing an exponent, so we give it the exponent 1.



-20 times  is  or just 

 in the parentheses on the left times  in the parentheses on the right
is  or , for we MULTIPLY by ADDING exponents.

 in the parentheses on the left times  in the parentheses on the right
is  or , for we MULTIPLY by ADDING exponents.

So the answer is 

Edwin

I'll do this one instead.  It's done exactly the same way as yours:



Make sure that every letter shows an exponent.  If a letter doesn't
have an exponent showing, give it the exponent 1:



For the first term:
3 times 5 is 15,  times  is  or .
so the 1st term is 
For the second term (not using the - in front:
12 time 7 is 84,  times  is  or .
so the 2nd term is 



Now since all the letters and exponents are the same in both those
terms, they are said to be LIKE TERMS, so we combine their coefficients
15-84 and get -69.

So the final answer is



Now do yours the exact same way.

Edwin