Answer:
That depends.
Now, if the person lost an eye and is blind in the other and it is multiplied by 10 then they'll have either 10 working or blind eyes.
If the person doesn't have any eyes and that is why the cannot see and you multiply by 10 then they will have 0 eyes.
If the person is blind with two eyes and that is why the cannot see and you multiply by 10 then they will have 20 working or blind eyes.
If you wanna play dumb then the person has 40 eyes.
Thanks for the sort of free points :D