Question 770249
Draw what you describe.  If your unknown side length is the number, c, then you can form an equation using Law of Cosines:


{{{highlight(300^2+c^2-2*c*300*cos(26)=150^2)}}}
{{{c^2-600*cos(26)c+300^2-150^2=0}}}      Quadratic Equation with Variable, c.
{{{c^2-539.28c+67500=0}}}

{{{c=(539.28+sqrt(539.28^2-4*67500))/2}}}
{{{c=(539.28+sqrt(20819.066))/2}}}
{{{c=341.784}}},
better to say based on provided accuracy
{{{highlight(c=342)}}}