San Mateo is about 2.2 times bigger than San Diego.
When you divide 960 by 430, (9.6 times 100 and 4.3 times 100) you get 2.23255813953, but since you’re supposed to round to the nearest tenth, that becomes 2.2. 430 times 2.2 is 946, but it’s close enough to 960 to be the correct answer.