Find the sum of the first 18 terms of the series 3, 6, 9,..., 36.

The seconds term of a geometric series is 4 while the fourth term is 16. Find the sum of the first five terms

A binary operation \(\oplus\) om real numbers is defined by x \(\oplus\) y = xy + x + y for two real numbers x and y. Find the value of 3 \(\oplus\) - \(\frac{2}{3}\).