Answer
Option ( C ) is correct i.e 3.5x+6 ≤ 85 .
Reason
As given in the question
x represented the pounds of propane delivered .
As given
Propane costs $3.50 per hundred pounds .
there is a $6 monthly delivery fee.
A family has budgeted $85 for their propane this month.
Than the equation becomes
3.5x+6 ≤ 85
Therefore option (C) is correct .
Hence proved