What denominator for 21/3=49/? would make these ratios proportional?

To make the ratios proportional, we need to find the denominator that would make the ratios equivalent.

In the given equation, we have:

21/3 = 49/x

To find the denominator, we need to find the value of x, which would satisfy the equation:

21/3 = 49/x

First, let's simplify the left side of the equation:

21/3 = 7

Now, the equation becomes:

7 = 49/x

To isolate x, we can cross-multiply:

7x = 49

x = 49/7

Therefore, the denominator that would make these ratios proportional is 7.