Question 1006805
n=number of checks; m=monthly fee; c=charge per check
.
cost of plan=m+cn
.
Plan A=$7.50+(0)n
Plan B=$3.00+$0.20n
.
When they cost the same, Plan A=Plan B:
$7.50+(0)n=$3.00+$0.20n
$7.50=$3.00+$0.20n
$4.50=$0.20n
22.5=n
The cost is the same when 22.5 checks are written,
so the fewest checks you must write for Plan A to 
be less expensive is 22.5.