Answer
$2$
Work Step by Step
Step 1. Given $f(x)=2x+9$, we have $f(x+h)=2(x+h)+9=2x+2h+9$
Step 2. $f(x+h)-f(x)=2(x+h)+9=2x+2h+9-2x-9=2h$
Step 3. Thus $\frac{f(x+h)-f(x)}{h}=2$
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