Observations have shown that at the moment the solar activity index, measured in Wolf numbers, is W = 123

Observations have shown that at the moment the solar activity index, measured in Wolf numbers, is W = 123, and the number of all sunspots on the Sun is f = 33. Determine the number of groups g on the solar disk, taking the factor k in the formula W = k (10g + f) equal to one

To find the number of groups, i.e. unknown from the above formula, it is necessary to substitute the values of known quantities into the formula. We will have 123 = 1 (10g + 33). Or 123 = 10g + 33. Or 10g = 90, Hence the number of groups g = 90/10 = 9 groups.