A: Tiana multiplied each number by -4, so she did:
B: Since Tiana is multiplying two negative numbers, the negatives will cancel each other out. So she would get positive 24 as her answer.
C: Amit's first step was correct, because you always do the equations inside parenthesis before anything else. The order you asses equations is parenthesis, exponents, multiplication and division, addition and subtraction. This can be remembered as PEMDAS.