Construct a triangle ABC in which base, BC = 6 cm; ∠B = 60° and sum of other two sides = 9 cm.

                              
Steps of Construction
(i) Draw BC = 6 cm.
(ii) Construct ∠CBX = 60°. 
(iii) With B as centre and radius 9 cm cut an arc on the ray BX at P.
(iv) Join CP.
(v) Draw the perpendicular bisector of CP to intersect BP at A.
(vi) Join AC.
Then, ABC is the required triangle.