Question 1171222
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If a formal algebraic solution is not required....<br>
The newer machine can do the job alone in 10 minutes.<br>
So when the two machines together do the job in 6 minutes, the newer machine does 6/10 = 3/5 of the job.<br>
That means in those 6 minutes the older machine does 2/5 of the job.<br>
2/5 of the job in 6 minutes means the older machine can do the whole job alone in (5/2)*6 = 15 minutes.<br>