If less than half of the garden is planted with corn, then is it reasonable to estimate that 5/6 of the garden is planted with corn?

No because that means that you are saying that LESS than half should be without corn so if it's less it should be either 2/5 or 1/5. 

Hang: ggffhgfgfggccffg

$250 deductible means jane must pay the first $250 of her bill. so the insurance company paid = (80% of bill) - deductible = (0.8 x $2550) - $250 = $2040 - $250 = $1790 and jane's cost is = (bill) - (insurance payment) = $2550 - $1790 = $760