Can someone help me solve parts (a) and (c) please? Thank you!

a) 6x + 6

b) 15 x 24

c) see explanation

Step-by-step explanation:

a) 2x + x + 3 + 2x + x + 3 = 6x + 6

b) 6x + 6 = 78

6x = 72

x = 12

2(12) = 24

(12) + 3 = 15

15 x 24

c) 2x(x + 3) = 2x² + 6x

2(12)² + 6(12) = 288 + 72 = 360

15 x 24 is also 360

f(x) = x^3 -2x^2 -3x

x( x^2 -2x-3)

x( x^2 +x -3x -3)

x( x(x+1) -3(x+1))

x( x-3)( x+1)

so zeroes are 0, 3,-1

its (2) option