Answer:
Let's denote Becky's age as B. The equation representing Johnny being three times as old as Becky is
J = 3B
Given that Johnny is 21 years old, substitute J with 21:
21 = 3B
Now, solve for Becky's age (B). Divide both sides of the equation by 3:
B = {21}{3}
Therefore, Becky is B = 7 years old.
