Given the following:
7 blue marbles
2 green marbles
1 red marbles
We to find the probability of not drawing a blue marble.
We will be solving it in two ways.
First let's get the total marbles
Total Marble = 7 + 2 + 1 = 10
recall that probablity is number of favourable outcome divide by number of total outcome.
So,
probablity of Drawing a Blue Marble is = 7/10
probability of not Drawing Blue Marbles = 1 - Probability of Drawing Blue Marbles
= 1 - 7/10
= 10 - 7
10
= 3/10
OR
Probability of not Drawing Blue Marbles = Probablity of drawing Green or Red Marbles.
= 2/10 + 1/10
= 3/10
Therefore, the probability of not Drawing Blue Marbles is 3/10.