Respuesta :

sqdancefan

Answer:

  x - 18 = 21

Step-by-step explanation:

In math, the description, "the difference between p and q" is written as ...

  p - q

Then the difference between x and 18 is ...

  x - 18

When we say that "is 21", we mean it is equal to 21:

  x - 18 = 21