36 sundaes were sold.
To show that this is correct, first subtract 8 from 36, to get 28. 28 is equal to the number of banana splits sold. Next, multiply 36 by 2, to get $72. Then, multiply 28 and 3 to get $84. Finally, add $72 and $84 to get $156. Thus proving that 36 sundaes were sold.
I hope this helps!