According to the meaning of the question

a-b=0

2b+c=0

c- 1/2=0

The simultaneous solutions are a=- 1/4, b=- 1/4 and c= 1/2.

therefore

a(b+c)

=(- 1/4)x(- 1/4+ 1/2)

=(- 1/4) x( 1/4)

=- 1/ 16