The coal

The coal stock would be enough to heat a larger room for 12 weeks, a smaller one for 18 weeks. It was heated for four weeks in both rooms, then only in a smaller one. How long was the coal stock enough?

Correct answer:

x =  12

Step-by-step explanation:

z=12a z=18b z4a4b=b x  z4(z/12)4 (z/18)=(z/18) (x4)  14 (1/12)4 (1/18)=1/18 (x4)  2x=24  x=12

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