I have a logarithm word problem that i am having problems with. not sure where to plug in the numbers and how to get my result. any help will be greatful.

it is a 2 part problem.

Measured on the richter scale, the magnitude of an earthquakes of intensity I is defined as R=log(I/I0), (that is an I with a base of 0 in the denominator) where I0 is the minimum level for comparison. a) what is the richter scale reading for an earthquake whose intensity was 83,000,000I0?

b) find the intensity I in terms of I0 of an earthquake that measured a 6.9 on the richter scale. (R=6.9)