<PRE><B>Question 1168237</B>
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Mark car consume 15 liters of gasoline to travel 150 kilometers.At that rate how much gasoline will his car use to travel 400 kilometers?
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{{{15/150=x/400}}}-------very simple proportion




For the next one maybe you mean like:

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Lucy is 12 years older than her sister Macy. Four years from now, Macy will be two third as old as Lucy.
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Simple algebra, or maybe just arithmetic</PRE>