How many times are fives subtracted from 15 to get 0?​

Can someone answer these problems for me

Acoin bank containing only dimes and quarters has 12 more dimes than quarters. the total value of the coins is $11. how many quarters and dimes are in the coin bank?

What are the values of a, b, and c in the quadratic equation 0 = x2 – 3x - 2? a = 1, b = 3, c = 2 a=, b = -3,c=-2 a = 1, b = 3, c= 2 a = 1.0= -3, c = 2