Answer:
236
Step-by-step explanation:
We assume the cost is a linear function of the number of lessons. That means the slope is the same everywhere.
Let (lessons, cost) = (x, y). We have (4, 84), (8, 160), (12, y3).
(y2 -y1)/(x2 -x1) = (y3 -y2)/(x3 -x2)
(160 -84)/(8 -4) = (y3 -160)/(12 -8)
76 = y3 -160
y3 = 160 +76 = 236
The cost will be $236 for 12 lessons.
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The cost function is ...
y = 19x +8 . . . . for x lessons
