A restaurant needs to order stools and chairs to be able to seat 36 people. Each stool has 3 legs and each chair has 4 legs. They ordered 129 plastic feet covers for the bottom of the legs to ensure the stools and chairs don't scratch the floor. How many chairs and how many stools did the restaurant order?

21 chairs and 17 stools

Step-by-step explanation:

let there be x and y stools and chairs respectively.

according to question

x+y =36i

and, 3x+4y= 129 ii

solving i and ii we get

y= 21 and x= 17

Therefore, the manager must order 21 chairs and 17 stools

2040 = n/2(20+(n-1)4)

4080 = n(20+4n-4)

4080= 20n +4n^2 -4n

1020 = 4n + n^2

n^2 +4n -1020 =0

use common formula (can't write out so just look at answers. sorry)

which gives answers of n=-34 and n=30. since n can only be positive, n=30 so there are 30 rows. I liked that challenge