How many carbon atoms are on the reactant side of the equation below?

The answer to your question is 6 carbons.

Explanation:

Chemical reaction

                   6CO₂  +  6H₂O   ⇒   C₆H₁₂O₆  +  6O₂

To calculate the number of atoms of an element in one side of the equation, multiply the coefficient (the number before the molecule) by the small number after the element.

Example

Number of carbons in the reactants

Coefficient = 6

Small number after the molecules = 1  (number one is not written in the

                                                                formula)

Number of carbons = 6 x 1 = 6