Answer
The required probability is, $\frac{7}{8}$
Work Step by Step
We know that the sample space of equally likely outcomes is $\left\{ MMM,MMF,MFM,MFF,FMM,FMF,FFM,FFF \right\}$
Thus $ n\left( S \right)=8$
Let $ E $ be the event of obtaining at least one male child; then $ E=\left\{ MMM,MMF,MFM,MFF,FMM,FMF,FFM \right\}$
Therefore, $ n\left( E \right)=7$
Thus, the probability of obtaining at least one male child is:
$\begin{align}
& P\left( E \right)=\frac{n\left( E \right)}{n\left( S \right)} \\
& =\frac{7}{8}
\end{align}$
