Question 34892
Here is the old way:

Starting at the decimal, separate the number into packets of 2 digits:
In your case break it as follows  5 \ 29.
Find  the largest perfect square less than or equal to the left-most packet.
That would be "4".
Write the square root of "4" to the left of 5\29
Divide 2 into the 5 and write the resulting 2 above the 5.
Multiply 2*2 and write the 4 below the 5.
Substract and bring down the next packet.
You now have 129 written two lines below the 529
Now it gets interesting.
Double the number written above the 529 and write 4_
(yes, that's 4_ )to the left of 129. 
Now think of a digit that you can write above the 
29 and to the right of the 4 in 4_ so that the product 
will be as large as possible but less than 129.
That digit is "3". because 3*43=129  Whoopee!
The number above the 529 is the square root of 529
sqrt(529)=23
Cheers,
Stan H.