To calculate the average,
first, for each row, multiply the number of families times the number of cars that they own:
2 · 0 = 0
8 · 1 = 8
x · 2 = 2x
2 · 3 = 6
second: add the totals from each row: 0 + 8 + 2x + 6 = 2x + 14
third: find the total number of families: 2 + 8 + x + 2 = x + 12
fourth: find the average by dividing the result of the second step by the result of the third step:
average = (2x + 14) / (x + 12)
fifth: set this average to the known average: (2x + 14) / (x + 12) = 4/3
sixth: solve this equation for x; this willbe your answer.