if log 10 x=3, then x =

log10(x)=3

You can write this as 10^3=x

Because logarithms find exponets, you can interchange between these to forms

LOGe(x)=i is the same as e^i=x

Now that im thinking about it, it may be wrong. CPhill will correct me.

Sorry for any errors

The base 10 log of a number is the exponent of 10 that will result in that number

log x    =      3        means   10^3 = x

x = 1000              

Because you are already given the log of x as being 3 to base 10, it follows that x=10^3=1000. Therefore, the answer is "B".