Evaluate:

​$$\sqrt{\left(42 + \sqrt{\left(40 + \sqrt{\left(74 + \sqrt{\left(42 + \sqrt{\left(49\right)}\right)}\right)}\right)}\right)}$$​​

Correct option is A

Given:

​$$\sqrt{\left(42 + \sqrt{\left(40 + \sqrt{\left(74 + \sqrt{\left(42 + \sqrt{\left(49\right)}\right)}\right)}\right)}\right)}$$​​

Solution:

​$$\sqrt{\left(42 + \sqrt{\left(40 + \sqrt{\left(74 + \sqrt{\left(42 + \sqrt{\left(49\right)}\right)}\right)}\right)}\right)} \\ \ \\ = \sqrt{\left(42 + \sqrt{\left(40 + \sqrt{\left(74 + \sqrt{\left(42 + 7\right)}\right)}\right)}\right)} \\ \ \\ = \sqrt{\left(42 + \sqrt{\left(40 + \sqrt{\left(74 + 7\right)}\right)}\right)} \\ \ \\ = \sqrt{\left(42 + \sqrt{\left(40 + 9\right)}\right)} \\ \ \\ = \sqrt{\left(42 + 7\right)} \\ \ \\ = \sqrt{\left(49\right)}\\ \ \\ = 7$$​​