Solution
We draw a venn diagram to illustrate the information
Without the loss of generality
From the question we have that
[tex]\begin{gathered} n(C\cup Ch)=78 \\ \\ 58-x+x+57-x=78 \\ \\ 115-x=78 \\ \\ x=115-78 \\ \\ x=37 \end{gathered}[/tex]
Therefore, the probability that a chosen customer carries both cash and checks is
[tex]\begin{gathered} p=\frac{37}{100} \\ \\ p=0.37 \end{gathered}[/tex]
The answer is
[tex]0.37[/tex]
