Question 308236
Plot a graph

{{{graph( 500, 500, -10, 10, -20, 20, abs( 3-6x ), 15 ) }}}

As always with absolute value questions, you need to solve two equations

3-6x=15 when 3-6x > 0
-(3-6x)=15 when 3-6x < 0. 

Work it out.