Question

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

Answer 1

29 red marbles

Explanation:

Call R the number of red marbles and B the number of black marbles.

According to the second sentence, R = 2B + 3.

According to the third sentence, R + B = 42.

Now we have 2 equations, 2 unknowns. Sub the first into the second since it already has R isolated:

2B + 3 + B = 42

3B = 39

B = 13

Now sub this into either of the original equations (I'll use the first):

R = 2(13) + 3

R = 29