(I) draw a line segment measure 15 cm and name it Y and Z
(II) draw angle at Y measure 30
(III) draw an angle measure 90' at Z
(IV) then draw the angle bisectors of Z and Y which will meet at K
(V) draw the perpendicular bisector of KY and KZ which meets YZ at L and M respectively
(VI) then join the point L and M to pint K
(VII) therefore KLM is the required triangle
i hope it helps..........