Question 289895
{{{3x(2x + 1) = 18}}}
{{{x(2x + 1) = 6}}}
{{{2x^2 + x = 6}}}
{{{2x^2 + x - 6=0}}}
It's a quadratic equation in x. 
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{{{ graph( 300, 300, -5, 5, -10, 10, 2x^2+x-6) }}}
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You can try solving by graphing, factoring, or using the quadratic equation to solve for x. 

{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
where
{{{a=2}}}
{{{b=1}}}
{{{c=-6}}}