The sales will be equal after 40 months.
In order to find this, use a system of equations where
s represents sales of scientific calculators
g represents sales of graphic calculators
x represents the number of months that have passed
s = 1500x + 10000
g = 1300x + 18000
s = g
1500x + 10000 = 1300x + 18000
Subtract 1300x and 10000 from both sides
200x = 8000
Divide each side by 200
x = 40
To graph this, use the expressions
f(x) = 1500x + 10000
g(x) = 1300x + 18000
where f(x) is scientific calculator sales and g(x) is graphic calculator sales
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A more complex method would be to graph the following
f(x) = 1500x + 10000
g(x) = 1300x + 18000
and find the point where they intersect. The x-value of that point is your answer (in months) of how long it will take for sales to intersect.
f(x) is the sales of scientific calculators
g(x) is the sales of graphic calculators
x is the number of months that have passed
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Hope this helps
