For this case, the first thing we must do is define a variable.
We have then:
n: number of days.
We now write the explicit formula that represents the problem.
We have then:
an = 4n + 15
Where,
15: crunches the first day
4: increase the number 4 each day
Answer:
An explicit formula for the number of crunches Abbie will do on day n is:
an = 4n + 15
