Let b be the price of the bath towels and h be price of the hand towels. For Helen, we can write the following equation
[tex]4b+3h=72[/tex]And for Althea, we have
[tex]3b+6h=84[/tex]Then, we have 2 equations in 2 unknowns. By multipliying the first equation by -2, we have the following equivalent system of equation
[tex]\begin{gathered} -8b-6h=-144 \\ 3b+6h=84 \end{gathered}[/tex]By adding both equations, we have
[tex]\begin{gathered} -5b+0=-60 \\ or \\ -5b=-60 \end{gathered}[/tex]Then, b is given by
[tex]\begin{gathered} b=\frac{-60}{-5} \\ b=12 \end{gathered}[/tex]Therefore, 1 bath towel cost $12, which corresponds to option 3