Since each week murray gives his parrents $2, each week the debt is 80-2t.
Since each week Melanie gives her parents $1, each week the debt is 55-t
[tex]\begin{gathered} \text{ We have to find the week t such that } \\ 80-2t=55-t \\ 80-55=2t-t \\ 25=t \end{gathered}[/tex]After 25 weeks melanie and murray will owe their parents the same amount of money!
at the week 25, Murray's debt wiill be
[tex]\begin{gathered} 80-2(25)=80-50 \\ =30 \end{gathered}[/tex]And we see that is equal to melanie's debt at that week!
[tex]55-25=30[/tex]