Solve the following riddle:
I am a number,
Tell my identity!
Take me seven times over
And add a fifty!
To reach a triple century
You still need forty!
Let the number be x.
(7x + 50) + 40 = 300
7x + 90 = 300
7x = 300 − 90 (Transposing 90 to R.H.S.)
7x = 210
Dividing both sides by 7,
x = 30
Therefore, the number is 30.