If the variance of 3+x, 6, 4, x and 7-x is 4 and the mean is 5, find the standard deviation

\(\begin{array}{c|c} Score & 3 & 4 & 5 & 6 & 7 & 8 & 9 & 10 \\ \hline Frequency & 1 & 0 & 7 & 5 & 2 & 3 & 1 & 1 \end{array}\)
The table above shows the scores of 20 students in further mathematics test. What is the range of the distribution?

In how many ways can a student select 2 subjects from 5 subjects?

In how many ways can 3 seats be occupied if 5 people are willing to sit?

What is the probability that an integer x \((1 \leq x \leq 25)\) chosen at random is divisible by both 2 and 3?