Question 1186169
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Using the model suggested in your post....<br>
Let t = # of hours to complete the job<br>
(pages per hour of the first machine) * (# of hours to complete) + (pages per hour of the second machine) * (# of hours to complete) = (total pages)<br>
(1800)(t)+(2400)(t)=20(420)
1800t+2400t=8400
4200t=8400
t=8400/4200=2<br>
ANSWER: 2 hours<br>