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First calculate f(1) by substituting the value of 1 instead of x into the formula for f(x)
    f(1) = 3*1 + 2 = 3 + 2 = 5.
To find f(f(1)),  replace the interior f(1) by 5, since you just calculated it. 
You will get
    f(f(1)) = f(5) = 3*5 + 2 = 15 + 2 = 17.
ANSWER.  f(f(1)) = 17, and you know now how to find it.
Solved and explained.