Mean is the arithmatic average of a given data set. So,
[tex] Mean= \frac{Sum of the data}{Number of the data} [/tex]
There are seven data in the data set.
According to the given problem,
[tex] \frac{18+p+13+q+15+r+7 }{7} =11 [/tex]
[tex] \frac{53+p+q+r }{7} =11 [/tex] Combine the like terms of the numerator.
[tex] \frac{53+p+q+r }{7}*7 =11 *7 [/tex] Multiplying 7 to each sides of equation.
53 + p + q + r = 77
53 + p + q + r - 53 = 77 - 53 Subtract 53 from each sides.
p + q + r = 24
Next step is to divide each sides by 3 so that we can write this in form of mean of p, q and r. Therefore,
[tex] \frac{p + q + r}{3} =\frac{24}{3} [/tex]
So, mean of p, q and r = 8.
I hope this helps you!.
