Answer and commentary
To work out the mean average we need to know the total number of cars and divide by the number of families.
The first column shows 3 families with 0 cars each that's 3 x 0 = 0 cars!
Actually it is useful to carry on in this way because the total will be:
3 x 0 + 8 x 1 + 5 x 2 + 2 x 3 + 1 x 4 = 0 + 8 + 10 + 6 + 4 = 28.
There are 3 + 8 + 5 + 2 + 1 = 19 families.
So, the mean average is 28 ÷ 19 = 1.473684... cars.

Written to a reasonable 1 decimal place that's 1.5 cars.

Answer: 1.5 cars.