To determine if all three of those fractions have the same decimal equivalent, we simply divide the numerator by the denominator. Fractions mean division!
So for the first one 21/3 - That's 21 divided by 3. That's 7!
The second one 120/12 - That's 120 divided by 12. That's 10!
The last one - 7/9 - That's 7 divided by 9. That's .7777 or rounded out is .78!
So all three of those fractions do not have the same decimal equivalent