We know that for any number of mutually exclusive events, we have the formula:
[tex]P(A_1\cup A_2\cup A_3\cup\ldots)=P(A_1)+P(A_2)+P(A_3)+\cdots[/tex]In this case, we have that P(A)=0.60 and P(B)=0.30, then:
[tex]\begin{gathered} P(A\cup B)=P(A)+P(B)=0.60+0.30=0.90 \\ P(A\cup B)=0.90 \end{gathered}[/tex]Therefore, P(A or B) =0.90
