HELP ME!! I don’t understand the correct answer is 1/6 but I tried it and I got 1/4 then I tried it again and then I got 2/3 I am very confusions!! Please Explain.

HELP ME I dont understand the correct answer is 16 but I tried it and I got 14 then I tried it again and then I got 23 I am very confusions Please Explain class=