Respuesta :

18+27f-39 *distribute*
27f-21 *add like terms*
First, you want to use the distributive property on 3(9f - 13): 

18 + 27f - 39 

Then, you need to subtract 18 from 39 (you will get a negaitve number): 

27f - 21 
Your answer should be the bottom left one: 27f - 21
Hopefully that helped! :)