The answer is 17.5.
To do this, first I’d work out 10% of 50. To do this, divide 50 by 10. (Because you’re getting from 100% to 10%, and to do that you divide by 10, meaning you need to do the same for the 50)
This gives 5. You need 3 of those to get 30, so multiply 5 by 3.
This gives 30% = 15
Then the remaining 5% can be found by halving the 10% we had, which was 5. Half of 5 is 2.5.
Then you add 30% and 5% to get 35%, giving 15 + 2.5, which equals 17.5.
