This question involves the Richter's scale and it goes like this:

According to Richter's scale magnitudes of earthquakes can be obtained from the following formula:
M=logE÷1.44-3.64 .
E stands for the free energy of a 6.4 earthquake ,calculate the magnitude of this earthquake if the free energy is 200

first you have to use a table or a calculator to find the log of 200. Put that result into the formula given.