either a student passes an exam or fails it. that means the percentage of students who pass plus the percentage of students who fail must add to 100%. this also means that if 22% pass, then 78% fail. there are 68 students total and 78% fail so the number of students failing is:
(78/100)(68) = 53.04 which is approximately 53 students.
let me know if you have any questions!!!!