Keep getting mixed answers Which equation is equivalent to the formula m = ca?

a = cm
a equals m over c
c = am
c equals a over m

everyone is saying 1 or 3, which one is right?

What can you determine about the solutions of this system

The median of a data set is the measure of center that is found by adding the data values and dividing the total by the number of data values that is the value that occurs with the greatest frequency that is the value midway between the maximum and minimum values in the original data set that is the middle value when the original data values are arranged in order of increasing (or decreasing) magnitude

Which is the scale factor proportion for the enlargement shown?