Answer:31
Step-by-step explanation:I would use my fingers mostly.
But, I just do it normally. I pretend I'm using a sheet of paper then I write on it for the equation.
903.6 divided by 29.1
Then I estimate it because I know that 29.1 can go into 903.6 about 31 times. Then I multiply 31 and 29.1 and i get around 903.6.
I hope this helps. I'm sorry if you get this wrong.