9/15 as a percent is 60%, so D.
4 1/5 as a percent is 420%, so B.
101 child tickets were sold that day
There are 4 positions in the string that each have 25 choices (any letter in the English alphabet except A) and the other positions are filled with A, so there are 25⁴ possible strings containing exactly 7 A's.
Overall, there are 26¹¹ possible strings of length 11.
Then the probability of randomly generating a string containing exactly 7 A's is
25⁴ / 26¹¹ ≈ 0.000000000106427
all you have to do next is add all of them in one equation and equate them to 18
when you find x, replace in each expression to get your answers
