Ok you bring the power to the front and take 1 away like normal differentiation. You then multipply it by whatever is in the bracket differentiated.

so a would be 5(2x^2 - 3x + 1)^4 *(4x-3)

=(20x-15)(2x^2 - 3x + 1)^4

i think that right

try it with b

for c i think you just have to know that cosecx is -cosecxcotx