We need to find the he probability of drawing a red or green marble
8 blue marbles
5 green marbles
8 red marbles
8 + 5 +8 = 21 total of marbles
To find probability of drawing a red or green marble
use the formula of probability: P = favorable outcome / total outcome
The P of get a blue marble is P(B) = 8 / 21
The P of get a red marble is P(G) = 8 / 21
The probability of get blue or red is the sum of the two P(B) and P(G)
P(B) + P(G) = 8/21 + 8/21 = 16/21
So the probability of drawing a red or green marble is 16/21