Please answer the following question, thank you very much?

a)
x(x-2)<80 and x-2>0
x²-2x-80<0 and x>2
(x-1O)(x+8)<0 and x>2
-8<x<1O and x>2
2<x<1O

b)
2<x<1O and x is an integer
x = 3,4,5,6,7,8 or 9
So the max. length of the metal wire is 9+2(9-2) = 23cm