How do you find the answer for this:

Question

Pam is playing with red and black marbles. The number of red marbles she has is three more than twice the number of black marbles she has. She has 42 marbles in all. How many red marbles does Pam have?

a. 13
b. 15
c. 29
d. 33

Answer 1

Let R = # red marbles
and B = # black marbles.
===========================
R + B = 42
R = 3B + 3
Solve the two equations.
I have 13 for B and 29 for R but check me out. Check my work. Check my thinking.

Answer 2

thanks