Let us say company a charges y $ for harvesting x hectares than we have relation

y = 6x +20

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For Company B..considering that they charge Y$ for x hectares than we have relation

y= 3X + 35

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Draw these graphs...

The point of intersetion is the point where for a particular x

y charged by Company A =y charged by company B

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You should always post your try with every question... than we have a better idea of where you got struck.