Which one of the following statements expresses a true proportion?
a. 14 : 6 = 28 : 18
b. 3 : 5 = 12 : 20
c. 42 : 7 = 6 : 2
d. 2 : 3 = 3 : 2

I’m stuck on this i don’t understand.

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)

Which are factor pairs of 350? choose all answers that are correct. a) 30 and 12 b) 35 and 10 c) 70 and 5 d) 2 and 125