SOLUTION: a wholesale poster company sells 20 posters for $12 and 30 posters for $15 the relationship between the number of posters sold and the cost is linear. find an equation giving the c

Question 762911: a wholesale poster company sells 20 posters for $12 and 30 posters for $15 the relationship between the number of posters sold and the cost is linear. find an equation giving the cost (c) in terms of the number of(n)posters
Answer by malglu(63) (Show Source): You can put this solution on YOUR website!
since the relationship is linear we know that we plot the relationship on a co-ordinate system. we would have a line going through the points
(20, 12) and (30, 15)
if we fill in the x and y co-ordinates on the equation for a line
y=mx+c we get teo equations which can be solves simultaneously
15=30m+c
12=20m+c
minus one from the other, to get m=3/10
fill this in into any of the two equtions to get c, whcih is 6.
thus the realtionship, is the linear equation
y=3/10x+6
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