Hello there! For these kinds of proportions, all you have to do is cross multiply the values and then divide them by each side to isolate the variable. Here are the answers worked out.
A: Cross multiply the values to get 7x = 252. Divide each side by 7 to isolate the variable and you get x = 36. 36 > 4. A is eliminated.
B. Cross multiply the values to get 84 = 21x. Dive each side by 21 and you get x = 4. 4 = 4. Score! But let's try the others out.
C: Cross multiply the values in order to get 5x = 2. Divide each side by 5 to isolate the variable and you get x = 2/5. 2/5 < 4. C is eliminated.
D: Cross multiply the values to get 5x = 200. Divide each side by 5 to isolate the variable and you get x = 40. 40 > 4. D is eliminated.
The only answer choice that works here is B. The answer is B.
