Yup

Wrong

Sorry

It’s ah/a=h

Amp hours divided by amps = hours

So your example would be

10/8=1.25 hrs

Sorry, but I just checked online to find the formula I mentioned, and it is:

The formula is 10 x battery capacity in Amp hours divided by load power (device power draw).

So a 12v 9ah battery and a 10.5 W fish finder would be 10 x 9 / 10.5 or 8.5 hours.

(kind of a "right church, wrong pew" scenario)