Work Step by Step
According to the first Rule for a Discrete Probability Distribution (see page 323): $∑P(x)=1$ $P(3)+P(4)+P(5)+P(6)=1$ $0.4+P(4)+0.1+0.2=1$ $P(4)=1-0.4-0.1-0.2$ $P(4)=0.3$ Notice that: $0\leq P(4)\leq1$ (second Rule)
You can help us out by revising, improving and updating this answer.Update this answer
After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.