Let Harris family used their sprinkler for x hours and Carter family used their sprinkler for y hours.
Then the equation for total time of sprinkler use is,
[tex]\begin{gathered} x+y=55 \\ y=55-x \end{gathered}[/tex]
Determine the equation for total water output from both the sprinkler.
[tex]\begin{gathered} 25x+15y=1075 \\ 5x+3y=215 \end{gathered}[/tex]
Substitute 55-x for y in the equation to eliminate the y terms.
[tex]\begin{gathered} 5x+3(55-x)=215 \\ 5x+165-3x=215 \\ 2x=50 \\ x=25 \end{gathered}[/tex]
Substitute 25 for x in the equation y=55-x to obtain the value of y.
[tex]\begin{gathered} y=55-25 \\ =30 \end{gathered}[/tex]
So Harris family used sprinkler for 25 hours and Carter family used sprinkler for 30 hours.