Which two ratios represent quantities that are proportional help i will mark as brainless

A

Step-by-step explanation:

So, lets take all of our ratios, and simplfy them the best we can. Once we do this, we can easily compare and see which ratios are and are not similar.

So lets start with A:

21/28 and 12/16

Lets simplfy each fraction.

The greatest number that goes into the numeraotr and denominator(GCF) of 21/27 is 7. Taking out 7 we get:

3/4

We can do the same with the 12/16. 4 goes into both the numerator and denominator:

3/4

So this would work.

Lets look at the others, and see if any others work as well:

56/64 and 36/48

8 goes into both 56 and 64:

7/8

4 goes into 36 and 48:

9/12

These are clearly different.

Next we have 9/10 and 10/9

We can instantly see that one is bigger than 1, and the other is smaller than 1, so they must be different.

Finally we have 5/7 and 7/14

Again, these are clearly different.

If we give both the same denominator, which can be 14, we get:

10/14 and 7/14

We get 10/14 from 5/7 since we need to multiply both numerator and denominator by 2 so that the 7 becomes 14 in the denominator.

10/14 adn 7/14 are clearly different, so these dont work as well.

Only A, which is 21/28 and 12/16, will work.

Hope this helps!