Step-by-step explanation:
The total number of students is
![n(S)=35](https://img.qammunity.org/2023/formulas/mathematics/college/qfwmivrdltpa06jb1p8soctink76oqm63n.png)
Concept:
To figure out the probability that a student earns grade A,B or C
Will be calculated below as
![P(A,BorC)=P(A)+P(B)+P(C)](https://img.qammunity.org/2023/formulas/mathematics/college/nw7vl16gte153l43w35x81gpuj7hr7k8p0.png)
The Probability of A is
![P(A)=(n(A))/(n(S))=(5)/(35)](https://img.qammunity.org/2023/formulas/mathematics/college/e6ouho5pqalxw684er2tmckqlvjj8b1uq2.png)
The probabaility of B is
![P(B)=(n(B))/(n(S))=(10)/(35)](https://img.qammunity.org/2023/formulas/mathematics/college/hc5n53rtu3xvidyqmp114qye9zj5z36im3.png)
The probabaility of C is
![P(B)=(n(B))/(n(S))=(15)/(35)](https://img.qammunity.org/2023/formulas/mathematics/college/nt07b26892qqodfhkp5c4ousnmglu5ymv5.png)
Hence,
By substituting the values in the concept, we will have
![\begin{gathered} P(A,BorC)=P(A)+P(B)+P(C) \\ P(A,BorC)=(5)/(35)+(10)/(35)+(15)/(35)=(30)/(35) \\ P(A,BorC)=0.857 \\ P(A,BorC)\approx0.86(nearest\text{ }hundredth) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/zgdcm5ic89nt7z9ra4ph2obnqef6hkgwm3.png)
Hence,
The final answer is
![0.86](https://img.qammunity.org/2023/formulas/mathematics/college/sd241co6fwq25x6c0o7yq2mnrfhicri10s.png)