Answer
$0.7$
Work Step by Step
We know that by the addition rule of probabilities
$P(A\cup B)=P(A)+P(B)-P(A\cap B)$
If $A$ and $B$ are mutually exclusive, then $P(A\cap B)=0.$
Hence ,
$P(A\cup B)=0.25+0.45-0=0.7$
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