Since lines <em>a</em> and <em>b</em> are parallel and they are intersected by one line, the angles created by the intersection of both lines are equal.
So, since angle <em>t</em> is equal to the value of the angle corresponding to it, <em>t </em>= 158°.
To find the value of angle <em>s</em>, you need to subtract 158 from 180 (the angle of a straight line).