The size of a quantity first doubles and then increases by a further 16%. After a short time its size decreases by 16%. What is the net increases in size of the quantity?

The following table relates the number of objects f corresponding to a certain size x. What is the average size of an object?
\(\begin{array}{c|c} f & 1 & 2 & 3 & 4 & 5 \\ \hline x & 1 & 2 & 4 & 8 & 16\end{array}\)

If y = x² - 2x - 3, Find the least value of y and corresponding value of x

A father is now three times as old as his son. Twelve years ago he was six times as old as his son. How old are the son and the father?