$F$ is a finite measure on $(X,A)$
$a$ and $b$ belong to $A$
show that $F(a \cup b)=F(a)+F(b)-F(a \cap b)$
I have no idea how to approach this question. Any assistance would be appreciated.
$F$ is a finite measure on $(X,A)$
$a$ and $b$ belong to $A$
show that $F(a \cup b)=F(a)+F(b)-F(a \cap b)$
I have no idea how to approach this question. Any assistance would be appreciated.