-1/2=sin((pi*x)/(11));

1. Isolate x:  arcsin(-1/2) = pi*x/11;

-1/2  =  sin( πx/11 )

Find the invsin of both sides:  invsin(-1/2)  =   πx/11

Multiply both sides by 11 and divide by π   --->   (11/π)invsin(-1/2)  =  x

(When you finish this, remember that there are two answers, one in Quadrant III and the other in Quadrant IV.)

thank you!!!