Answer:
Teaching 25 students makes the teacher 100 dollars.
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Explanation:
The notation T(25) means "The value of T(x) when x = 25".
The instructions state that x represents the number of students. So x = 25 means the teacher has 25 students.
Writing T(25) = 100 means the teacher earns $100 from teaching 25 students.
We could also write T(x) = 100 when x = 25. Though it's more compact to say T(25) = 100.
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Note that,
T(x) = 4x
T(25) = 4*25 ... replace x with 25
T(25) = 100
As you can probably see by now, each student pays $4 which is what leads to the $100 total.
