The answer is:  10 x¹³ y¹⁰  . 
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1x^8 *  2y^(10) * 5x^5 = 
1* 2* 5 * x^8 * x^5 * y^(10) = 
10 * x^(8+5) * y^(10) =
10 * x^(13) * y^(10) = 10 x^(13) y^10 ;  write as: 
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          10 x¹³ y¹<span>⁰ .
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S = 2 * (pi) * r * h.....for r
divide both sides by 2 * pi * h
s / (2(pi)h = r
        
                    
             
        
        
        
You might want to check what I did just in case cause it's been a few years but it should be good. I hope this helps!
10.75 x 8.5 = 91.375
        
             
        
        
        
12 ribbons
p.s: im in 7th grade so you can trust me
        
                    
             
        
        
        
4. 15 tens, 1 hundred, 5 tens
150
5. 18 tens, 1 hundred, 8 tens
180
note: I hope this helps. I haven't done this in a long time. Sorry X(