Probability of A or B

$P$($A$ or $B$)=$P(A)-P(B)$

$P$($A$ or $B$)=$P(A)+P(B)$

$P$($A$ or $B$)=$P\left(A\right)\cdot P\left(B\right)$

$P$($A$ and $B$)=$P(A)+P(B)$