Answer :

Given a sample and required to get the probability of a particular outcome, we make a couple of considerations including:

- Sample Space: The universal set

- Required Outcome

We can identify these variables as:

Sample space: total number of marbles = 7

Required outcome: Not blue = 7 - 2 = 5

Probability is given as:

[tex]\begin{gathered} P=\text{ }\frac{\text{number of required outcome}}{Sample\text{ space}}=\frac{5}{7} \\ P=\frac{5}{7} \end{gathered}[/tex]