9, 9(2)=18, 9(3)=27, 9(4)=36 9(5)=45 9,18,27,36,45……..144 Not sure if this is what you are looking for. If the number of blanks is the amount of numbers allowed then the above will not work 9(13)=117, 9(14)=126, 9(15)= 135, 144 If you can only have 3 blanks then the second one could work. Again, not sure if this is what you need. But hopefully it helps.
The answer would be 20. Because the whole angle would have to be 90 so you already have 30 so that leaves you with 60 which you divide by 3 and gives you 20
