Answer:
f = d/(x+1)
Step-by-step explanation:
Factor out f, then divide by its coefficient.
[tex]d=f+fx\\\\d=f(1+x)\\\\\dfrac{d}{1+x}=f\\\\\boxed{f=\dfrac{d}{x+1}}[/tex]
_____
Additional comment
When writing this in plain text, parentheses are needed to perform the same grouping action that the fraction bar performs in a typeset expression:
f = d/(x+1)
