find missing input in function machine
Check the final answer first, then review the worked steps.
Problem
find missing input in function machine
Step-by-step solution
Let the operation be $f(x) = kx - 9$. For $x=5, f(5)=5k-9=31 \implies 5k=40 \implies k=8$. Testing $x=6, f(6)=8(6)-9=39$. Thus, for $f(A)=79, 8A-9=79 \implies 8A=88 \implies A=11$.
Answer
11