Let's go through each answer choice ------------------------------------ Choice A 5/12 = 7/15 5*15 = 12*7 ... cross multiply 75 = 84 The last equation is false so the first equation is false. This means choice A is NOT a proper proportion. We can eliminate choice A. ------------------------------------ Choice B 12/16 = 15/20 12*20 = 16*15 ... cross multiply 240 = 240 We have a true equation at the end (since we have the same value on both sides) so the first equation is true. This means choice B is a proper proportion. Note: both reduce to 3/4 which is 0.75 in decimal form. You can use a calculator to confirm.
We can stop here since we have the answer. However, for the sake of completeness, let's check the other answer choices. ------------------------------------ Choice C 8/32 = 1/3 8*3 = 32*1 ... cross multiply 24 = 32 We can eliminate choice C for similar reasons as done in choice A. ------------------------------------ Choice D 9/16 = 3/8 9*8 = 16*3 ... cross multiply 72 = 48 Similar to A and C, we can also eliminate D ------------------------------------ ------------------------------------