Let the number of mopeds be x
number of cars will be 3×x=3x
number of bicycles will be 2×3x=6x
Total number=number of mopes+number of cars+number of bicycles
=x+3x+6x=30
10x=30
x=3
hence the number of mopeds was 3, number of cars was 3×3=9, number of bicycle was 2×9=18