There is a logarithmic property that tells us how to simplify this.
log(10^100) = 100 * log(10)
In other words, if a logarithm's input is written as a power (like 10^100), we can move the exponent "out in front".
Stated symbolically, the property looks like this:
log(b^x) = x * log(b)
You can use this property to rewrite the given expression:
2 - log(10^100)
2 - 100 * log(10)
2 - 100
-98
Why are you clueless about logarithms ?
Do you know what an exponent is? Logarithms are just another way of writing an exponent.