Helena has $1.50 in dimes .she says i know i have 15 dimes because one dime is one a dollar

Which is the completely factored from of xy^3-x^3y

For f(x)=2x+3 and g(x)=x^2- 8 find (f+g) (x)

Jack has a piece of red ribbon that is two times as long as his piece of blue ribbon. he says that he can use two different equation to find out how long his piece of red ribbon is compared to his piece of blue ribbon is. is he correct? explain his reasoning