What does this Rebus Picture mean?

What am I?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

A California farmer owns a beautiful pear tree. He supplies the fruit to a nearby grocery store. The store owner calls the farmer to see how much fruit is available for him to buy. The farmer knows the main trunk has 24 branches. Each branch has exactly 12 boughs and each bough has exactly 6 twigs. Since each twig bears one piece of fruit, how many plums will the farmer be able to deliver?

Considering the below equation:

V + II - VI = 10
IV - X + VIII = 20
IV - VII + VI = 30

Then, I + II + III = ?

Count the number of balls in picture below:

What is the riddle which can be asked all day with a different correct answer each time.

Where do fish keep their money?

Which is heavier: a ton of bricks or a ton of feathers?

Can you convert the number zero(0) into a positive number using just one mathematical operator ?