334

The challenge for Class 2

Here's a challenge brought the girl from school.
Any idea how to solve it?



There is a correct answer, but how to come to it, I do not know.

Answer: 801

Source:
Pictures
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Russian ships, launched in 2013
...
King-car MB S-500 W222
...
The largest fleet of submarines
...
Whether to teach your child the system zhokhov
...
The world's 10 best cities to live. If you work in the Internet...
...
Triangle Karpman - space manipulation
...
The history of the legendary "Gelendwagen"
...
The best games of our childhood, we have lost
...
16 of the best games of our childhood
...
Fantastic Airbus A380
...
The best games of our childhood, we have lost
...
The best games of our childhood
...
Games of Soviet children (11 photos)
...
10 problems with the interviews in large companies
...
The best games of our childhood
...
Airbus A380 Fantastic (47 photos)
...
Empire Star Sword
...
How to find out its purpose by date of birth
...
To avoid financial problems, develop logic, gentlemen.
...
About 70
...
Ekaterina Burmistrova: 8 problem child in school
...
8 problem child at school: says family psychologist Catherine Burmistrov
...
The largest dump truck in the world (24 photos)
...
History of Volkswagen
...
Something about the Titanic
 Meet the new boss ...  In what has become Paris