Final answer:
The explicit formula to calculate Eleri's charge for the 8th grass-cutting service is a8 = 35 + (8 - 1)(-3), which simplifies to a8 = 35 - 21, resulting in a charge of $14.
Step-by-step explanation:
The student's question is about finding an explicit formula for calculating the charge for mowing grass with a discount applied each time.
To find the amount Eleri charges for cutting the grass for the 8th time, we need an arithmetic sequence formula, which typically has the form an = a1 + (n - 1)d, where an is the nth term, a1 is the first term, n is the term number, and d is the common difference between the terms. In this case, the first term a1 is $35, the term number n is 8, and the common difference d is -$3 (because the price decreases by $3 each time).
The explicit formula is a8 = 35 + (8 - 1)(-3), so the charge on the 8th time would be a8 = 35 + 7(-3).
Simplifying that, we get a8 = 35 - 21 = $14. Therefore, Eleri will charge $14 to cut the grass for the 8th time.