The square of a number is 19 less than twice of 50. What is the number?

Twice of 50 means 2 × 50 i.e. 100

Let the number be x.

The square of the number = 100 − 19

Thus, x² = 81

Taking square roots on both sides:

x = $\sqrt{81}$

Thus,  $\sqrt{81}$= 9                      (As 9² = 81)

Thus, the number is 9.