Answer:
[tex]\frac{2}{9}[/tex]
Step-by-step explanation:
The probability of an event is calculated by dividing the number of successful outcomes by the number of total outcomes. In an algebraic expression, that would be [tex]\frac{successful}{total}[/tex].
In this case, there are a total of [tex]20+15+10=45[/tex] ways to choose any ball, since there are [tex]45[/tex] balls in the box. However, only [tex]10[/tex] are yellow, so there are [tex]10[/tex] ways to successfully choose a yellow ball. Therefore, the probability of choosing a yellow ball is [tex]\frac{10}{45}=\frac{2}{9}[/tex]. Hope this helps!