What you need to do for this is evaluate your function for the value term (a + 1). What I mean by this is if F(x) is your function and you want to find F(A+1) plug in (a+1) into the equation where ever you see an x. In your function you have 3(x+1) + 1. Now use the distributive property to multiply 3 to both terms to obtain 3x + 3 + 1. Simplify and you now obtain F(a+1) = 3x + 4. For more detailed explanation visit my youtube channel http://www.youtube.com/mrbrianmclogan and search evaluating functions . Let me know if this helps.