C - cost; Â x - the number of chairs produced;
Linear equation: y = m x + b  ( m = ?, b = ? )
2200  = 100 m  + b  / * ( -1 )(we will multiply both sides of the equation by -1)Â
4000 = 300 m + b
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- 2200 = - 100 m - b
+
 4000 =  300 m + b
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1800 = 200 m
m = 1800 : 200 , Â m = 9 ( we will then plug in the first equation )
2200 = 9 * 100 + b
2200 = 900 + b
b = 2200 - 900, Â m = 1300
Answer: Â C = 9 x + 1300