hey i got 3 questions on an assignment, which i don't know how to do can anyone help me. they all need simplifying

a) 10y + (y-+7)(y-5) + 4y(to the power of 2)

b) 7z - (4a - 2z) - 6a(3a + 4z)

c) 4m(to the power of 2) - (10m + 4) to the power of 2

thanks to anyone who can answer and explain!