Brain teaser: Only a genius can solve this maths puzzle

A math brainteaser has recently taken the attention of puzzle enthusiasts, leaving many Brits scratching their heads. Are you a person who can easily solve large sums in your head, like a human calculator? If so, this challenge could be the perfect test to push your math skills to the limit. The puzzle has proven so difficult that 99% of people who attempt it can’t solve it, making it a true test of

numerical prowess

.
If you think you’re a math genius or feel you have the sharp mind of a modern-day Albert Einstein, now is the time to prove it. Don’t be fooled, though; although the sums appear simple at first glance, there’s something off about them, making this more challenging than it seems.
The puzzle takes the form of a series of math sums that look simplistic but don’t seem to add up. The difference is in recognizing the hidden pattern or logic behind the sum, which is not apparent at first.
The natures of the puzzle try to trick the eye into believing that it’s one thing when, in fact, it’s something else completely unless you catch the hidden rule.

There is no pressure in solving it, and therefore you can take time, concentrating on trying to understand the puzzle. You could need to get a pen and paper to work out step-by-step the sums since this might help break the challenge down and point out patterns you may have overlooked.
Stuck and close to giving up? Maybe you have finally cracked it. If you feel frustrated, do not worry. Please scroll down to the very end of the article in order to find the correct answer and see how did you do.
ANSWER: 77