how do i get the right answer

a = 30,

b = .5

c = -6

equation given:   (ab - c^2)/a - bc

substitute the values given:

(30(.)^2)/30 - .5(-6)

solve:

(15 + 6^2) / 30 - 3

(15 + 36 ) / 27

51 / 27

or simplified:

51/27 /3 = 17/9

or decimal:

1.

correct answer:

i^31 = -i

the answer would be 150 books

step-by-step explanation:

if you divide 300 by 2 you will get 150