Please help! I’ll give brianliest to the correct answer!

y = 1.5x + 9  

(y = height; x = number of cups)

Step-by-step explanation:

let x = number of cups

let y = height of the stack

the first cup will add 9 to the height (7.5 + 1.5)

so 9 is the y-intercept

for each additional cup, 1.5 will be added

so y = 1.5x + 9

the 8 in 8,420 is in the thousands place so it's value is 8 thousand.

the 8 in 6,870 is in the hundreds place so it's value is 8 hundred.

divide 8000 by 800 to find the answer:

8000 / 800 = 10

the 8 in 8,420 is 10 times greater than the 8 in 6,870