a) -20 - 10(-0.1)^2
= -20 - 10(0.01)
= -20 - 0.1
= -20.1

b) 7(-1)^3 - 4(-1)^2 - 8
= 7(-1) - 41 - 8
= -7 - 4 - 8
= -15

c) -10(-0.3)^2 - 5(-0.3) + 1
= -10*0.09 + 1.5 + 1
= -0.9 + 1.5 + 1
= 1.6