To determine whether or not these are proportional, take the two side lengths that are given and create a ratio. 6cm:3.5cm. I suggest writing this in fraction form to better see the equivalency. If you divide both 6cm and 3.5 cm by 2, you create an equivalent ratio of 3 cm:1.75cm. This is answer A. There is another correct answer too! If you take 6cm:3.5cm and multiple both by 1.5, it will create an equivalent ratio of 9cm:5.25 cm (answer choice E), just in a different order.