Answers
1.1) So, we're given that 6cm is 15 ft to scale. That means that every 2cm = 5ft. So, the dimensions of her room are 5ft x 10ft.
1.2) In square feet that makes 15 (length*width)
1.3) We want a 3-foot wide couch (1/5 of 15) which means it will be 1/5 of 6cm, which equals 1.2 cm wide.