We need to first figure the total salaries of both cities and then divide by the total employees of both cities to get the answer.
(137 x 67.013) + (25 x $71.332)
9180.781 + 1783.300 = 10964.081 salaries
137 + 25 = 162 people
10964.081/162 = 67.680 (rounded) average salary.