Five time of a positive integer is equal to 3 less than twice the square of that number. Find the number?

Let the number be N.
According to the question,
⇒ 5N = 2N² - 3
⇒ 2N² - 5N - 3 = 0
⇒ (N - 3) ( 2N + 1 ) = 0
N = 3 and N = -1/2
Thus, the required number is 3.