How can I solve this problem? 4/6 minus 2/9?

In the image, point a marks the center of the circle. which two lengths must form a ratio of 1 : 2? (options are in the images since thought they were harmful phrases)

20 da is equal to a. 2,000 cm. b. 2 m. c. 20,000 cm. d. 20,000 mm

Evaluate each expression. determine if the final simplified form of the expression is positive or negative -42 (-4)2 42