Print it :
$21 per jersey
x = number of jerseys
y = total cost
y= 21x
Top print
Setting up cost = $45
$18 per jersey
y= 45+18x
Equal both costs:
21x = 45 + 18x
Solve for x:
21x-18x =45
3x =45
x =45/3
x=15
when 15 jerseys are bought, both companies have the same cost.
If he bought more than 15 ( for example 20)
Print it = 21x = 21 (20)= 420
Top print = 45 +18 (20) = 405
Less than 15 jerseys ( ex: 10)
PRINT IT = 21 (10) = $210
TOP PRINT = 45+18(10) = $225
1.
When he buys more than 15 jerseys, he should choose TOP PRINT.
When he buys less than 15 jerseys, he should choose PRINT IT
2. set up one-off set up cost less than TOP PRINT = ex = 15
And a cost per shirt higher than TOP PRINT and less than PRINT IT = ex = 20 ( the slope value must be between 18 and 21 )