Can someone answer a and b to the file attached?

Explanation:

The equation of the reaction is given as;

12C + 16 H2 --> 4 C3H8

a. Simplify the equation;

The coefficients are 12, 16 and 4.

4 is a common factor, so divide all through by 4.

12/4 = 3, 16/4 = 4, 4/4 = 1

The equation is given as;

3 C + 4 H2 -->  C3H8

b. If 21 moles of  C3H8 are formed, how many moles of C was needed.

From the reaction;

3 mol C atoms reacts to form 1 mol of  C3H8

x mol would react to form 21 moles of  C3H8

3 = 1

x = 21

x = 21  * 3

x = 63 moles

the right answer is c i just did the question.