Marks	3	4	5	6	7	8
Frequency	5	x - 1	x	9	4	1
fx	15	4x - 4	5x	54	28	8

\(\sum fx = 15 + 4x - 4 + 5x + 54 + 28 + 8 = 101 + 9x\)
\(\sum f = 5 + x - 1 + x + 9 + 4 + 1 = 18 + 2x\)
\(\bar{x} = \frac{\sum fx}{\sum f}\)
\(5 = \frac{101 + 9x}{18 + 2x} \implies 101 + 9x = 5(18 + 2x)\)
\(101 + 9x = 90 + 10x \implies 101 - 90 = 10x - 9x\)
\(11 = x \)
(b)(i) Mode = 5.
(ii) Median
Frequency = 18 + 2(11) = 40.
Median position = \(\frac{40}{2} = 20\)
20th position = 5.
(c) No of students that scored at least 7 marks = 4 + 1 = 5.
Probability of scoring at least 7 marks = \(\frac{5}{40} = \frac{1}{8}\)