Both ratios simplify to the same numbers, they form a proportion.
To determine whether each pair of ratios forms a proportion, they have to express the same relationship between numbers.
When the ratios are equivalent after simplification, they form a proportion. Let's evaluate the given ratios:
For the pair 12/7 and 36/21, simplify the second ratio by dividing both numerator and denominator by the same number, 3 in this case:
36 ÷ 3 = 12
21 ÷ 3 = 7
So, 36/21 simplifies to 12/7. Since both ratios simplify to the same numbers, they form a proportion.