If we are finding 10% the cost of the item
you would set a proportion
or an easier way would be
.10x65
6.5
then you subtract that from 65
65-6.5
58.50 is the cost of the item 10% off but with shipping, it would be
58.50+7.25
65.75 is when there is 10% of the item
but it is $65 only if the shipping is free
and since 65<65.75
It is cheaper when the shipping is free