Drew has 50 red, green, and blue marbles. He has six more red marbles than blue marbles and four fewer green marbles than blue marbles. What will this equation look like?
a. ( R = B + 6, G = B - 4, R + G + B = 50 )
b. ( R = B + 6, G = B - 4, R - G - B = 50 )
c. ( R = B - 6, G = B + 4, R + G + B = 50 )
d. ( R = B - 6, G = B + 4, R - G - B = 50 )