Does anyone know this??

21

Step-by-step explanation: To solve this problem, we can first set up a proportion because we know that 3 is to 7 as 9 is to x.

So we have .

Now, we can use cross products to find the missing value.

So we have 3 time x which is 3x and 7 times 9 which is 63.

Rewriting our equation, we have 3x = 63.

Dividing both sides by 3, we find that x = 21.

So, x = 21.

The red arrows in the middle mean that they are parallel so the slopes are the same.

i believe the answer is c.

step-by-step explanation: it is d