A. In an equilateral triangle, all side are equal.

So, in triangle ABC, AB = BC = CA = 6 cm

Steps of Construction:

1. Draw a line segment BC of length 6 cm

2. Taking point B as center, draw an arc of 6 cm radius

3. Taking point C as center, draw an arc of 6 cm radius to meet the previous arc at point A

4. Join A to B and C

Now, ABC is the required equilateral triangle.

B. In an equilateral triangle, all side are equal.

So, in triangle PQR, PQ = QR = RP = 8 cm

Steps of Construction:

1. Draw a line segment QR of length 8 cm

2. Taking point Q as center, draw an arc of 8 cm radius

3. Taking point R as center, draw an arc of 8 cm radius to meet the previous arc at point P

4. Join P to Q and R

Now, PQR is the required equilateral triangle.