word problem with percentages Could you please explain to me how to solve this problem? In a city, $45\%$ of the population read magazine $A$, $55\%$ read magazine $B$ and $40\%$ read magazine $C$. $30\%$ read $A$ and $B$, $15\%$ read $A$ and $C$, $15\%$ read $B$ and $C$ and $10\%$ read all three magazines. How many percent read no magazine at all? [The answer is apparently $20\%$.]

Hint: You can apply the inclusion-exclusion-principle.

$P(A \cup B \cup C) =P(A)+P(B)+P(C)-P(A\cap B)-P(A \cap C)-P(C\cap B)+P(A\cap B\cap C )$

It is asked for

$1-P(A\cup B\cup C )$. But I have a result, which is different from 20%.