Question 975260
The sum of their probabilities equals 1 and they are mutually exclusive.
{{{P(A)+P(B)+P(C)=1}}}
{{{P(A)+2*P(A)+2*P(B)=1}}}
{{{P(A)+2*P(A)+4*P(A)=1}}}
{{{7*P(A)=1}}}
{{{P(A)=1/7}}}
Then,
{{{P(B)=2/7}}}
and
{{{P(C)=4/7}}}