If R= 5 Z Then 15 Z = 3 Y, The R=?

There are three variables in this question and I will derive the value of one and insert it in the other equation.

15z = 3y

y = 15z/3

y = 5z

or z = 0.2y

Putting the value of z in the equation:

R = 5(0.2z)

R = z

If 300 jellybeans cost you x dollars.  How many jellybeans can you purchase for 50 cents at the same cost?