Question 1152910
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<pre>

Let x be the time for Brooks, and y be the time for Wong.


The system of equations is


     x  +    y = 70       (1)  (the combined time)

    40x + 35*y = 2650     (2)  (liters total


To solve it, multiply equation (1) by 35 (both sides).  Keep equation (2) as is


    35x + 35y = 70*35      (3)

    40x + 35y = 2650       (4)


Now subtract equation (3) from equation (4). You will get


    40x - 35 x = 2650-70*35

      5x       =  200

       x       = 200/5 = 40.


<U>ANSWER</U>.   Brooks family - 40 hours; Wong family  70-40 = 30 hours.
</pre>

Solved.


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