Step 1
Write the sample space.
[tex]ttt,tht,tth,htt,hhh,hth,hht,thh[/tex]Therefore, the probability of getting 3 heads(hhh) is given as
[tex]\begin{gathered} \text{Probability}=\frac{number\text{ of required outcome}}{\text{Total number of outcomes}} \\ \text{Number of required outcomes = 1} \\ \text{Total number of outcomes = 8} \\ \text{The probability of tos}\sin g\text{ 3 heads(hhh)=}\frac{1}{8} \end{gathered}[/tex]Step 2
Find the probability of not tossing 3 heads with three fair coins is given as;
[tex]\begin{gathered} Pr(\text{not tossing 3 heads) = 1-pr(tossing 3 heads(hhh))} \\ Pr(\text{not tossing 3 heads) }=1-\frac{1}{8}=\frac{7}{8} \end{gathered}[/tex]Hence, the probability of not tossing 3 heads with three fair coins = 7/8