To find $ P(A) $ we use multiplication rule for independent events:

$$ \color{blue}{P(A \text{ and } B) = P(A) \cdot P(B)} $$

In this example we have:

$$ \begin{aligned} P(A \text{ and } B) &= P(A) \cdot P(B) \\ 0.3 &= P(A) \cdot 0.6 \\ P(A) &= \frac{ 0.3 }{ 0.6 } \\ P(A) &= 0.5 \end{aligned}$$

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