M=35
Here how it goes,
1/(2x2^35x5^35) = 1/5^m x 1/2^36 (since 1/4^18 = 1/2^36)
Now, we have same BASE, so we can ADD the powers.Therefore,
1/(2^36 x 5^35) = 1/2^36 x 1/5^m
compare. We get,
1/5^m = 1/5^35
M=35
Please refer to MGMAT Guides! They are awesome on this stuff!