How do you work these out im confused

Multiply 520 students by 20% (0.20).

520 * 0.20 = 104

Multiply 104 students by 12.5% (0.125).

104 * 0.125 = 13

13 students were on the wrestling team.

dimes (d) = n + .80, nickels (n) = n

Make the dimes and nickels add up to $1.40 in an equation.

(n + .80) + n = 1.40

Combine like terms.

2n + .80 = 1.40

Subtract .80 from both sides.

2n = 0.60

Divide both sides by 2.

n = 0.30

Divide this by 0.05 (how many nickels are in a dollar).

0.30/0.05 = 6

d = n + 0.80 ⇒ 0.30 + 0.80 = 1.10

Divide this by 0.10 (how many dimes are in a dollar).

1.10/0.10 = 11

There are 6 nickels and 11 dimes in the bank.

the rocket cannot penetrate the ground, in a contextual sense, therefore the roots of this equation should be the domain of this function. i'll let you find the roots of this quadratic equation (hint: use the quadratic formula:  

1- c

2-a

step-by-step explanation:

mark brainliest!