Actually you didn't.
It should have been 70%x.85+100%x.15
See below for your calc. I wonder if those who are paying for E85 realize they aren’t saving any money? If I remember correctly, ethanol is only 70% as efficient as gasoline. Which means a pretty good drop in mileage. Break even works out to $2.51/gal. (I took 70% of the price of gasoline to arrive at my figure.)
This thread is over a year old, give it a rest, will you?
I’m being kind at this point and will restrain from pointing out the fallacy of what you’ve just written.