Mork and mindy went to the garden center together to buy plants. mork bought 6 ferns and 1 azalea for $80. mindy bought 5 ferns and 3 azaleas for $84. what is the price of a single fern?

Convert the info into equations:

6f + a = 80
5f + 3a = 84

Then substitute one into the other, such that you eliminate one variable:

6f + a = 80 => a = 80-6f
5f+ 3(80-6f) = 84 => 5f + 240 - 18f = 84 => -13f = -156 => f=12

so the fern is $12.

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