Answer:
y = 15x + 85
Step-by-step explanation:
Let:
x = amount of months ; y = total amount
The constant is 85, meaning that this number will not change (for he would have at least 85 no matter how much time has passed).
15 is next to a variable, for depending on the amount of time passed, you will add a certain amount of "15" to the answer.
y is your total, and is also a variable, because it also depends on the amount of time that passes.
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