Step 1:

Draw ∠YBX = 60° and BC=5cm

Step 2:

With B as center and 7.5cm as radius draw an arc that intersects BY at Z.

Step 3:

Join CZ and then with C as center draw two arc at either side of the line CZ and repeat the same with Z as center.

Name the intersecting points as P and Q.

Step 4:

Name the intersecting point of PR and BZ as A and join AC.

So ABC is the required Triangle and here we can observe that AZ=AC (as AZC is isosceles).