Question

The set of lines $ax+by+c=0$ where $3a+2b+4c=0$ is concurrent at the point .....

Answer 1

Dividing by $4$, we get
$\frac{3}{4}a+\frac{1}{2}b+c=0$.
Compare with $ax+by+c=0$
Hence the set of lines pass through the point $(3/4,1/2)$.