Linear. They all follow the format y=mx+c wether or not they have been rearranged.
2.5 b = 27.5
b = 27.5 / 2.5
b = 11
You just need to substitute the the given function. So if f(-8) then you fill in f(n)=2n+4 which would be f(-8)=2(-8)+4. Which is -12.
hope this helps !
