Construct a triangle ABC in which BC=8cm , angle B = 60 degree , AB-AC = 3 cm

steps of construction:
1. draw base BC of 8 cm.
2. Construct an angle of 60 deg. at B by cutting an arc of any radius from point B marking it X and then with same radius, through X as centre, cut the arc on previous arc and join the point of intersection to B.
3. Extend that 60 deg. line to 3 cm from B. mark that point Y.
4. join YC
5. construct a perpendicular bisector of C.
6. wherever the bisector intersects BY, it is your point A.
7. join AC

You have your required triangle ABC constructed. Verify by measuring angle B with protractor and measuring the sides with ruler to find out the accuracy of sides and required difference.

Hope this helps!