The equation x - sin x = a has to be solved for x. x is in radians and a is a constant.

x - sin x = a

=> x - a = sin x

The plot of sin x is :

As the true value of x is not known, it is not possible to plot the graph of x - a. If the graph is plotted with the graph of sin x, the x-coordinate of the point of contact of the two graphs is the solution of the equation x - sin x = a.