Answer :
(a) No
[tex]f(x) = 12 - 5x[/tex]
[tex]f(0) = 12 - 5(0)[/tex]
[tex]f(x) = 12 - 0[/tex]
[tex]f(x) = 12[/tex]
Hence,
f(0) is unequal to 0.
(b)
[tex]f(x) = 12 - 5x[/tex]
[tex]f( - 1) = 12 - 5( - 1)[/tex]
[tex]f( - 1) = 12 + 5[/tex]
[tex]f( - 1) = 17[/tex]
(c)
[tex]f(x) = 12 - 5x[/tex]
[tex]f(x) = 6[/tex]
[tex]6 = 12 - 5x[/tex]
[tex]6 - 12 = - 5x[/tex]
[tex] - 6 = - 5x[/tex]
[tex]6 = 5x[/tex]
[tex] \frac{6}{5} = x[/tex]