Please answer the following question by reasoning step-by-step.
In four years, Suzy will be twice Mary's age then. If Suzy is 20 now, how old is Mary?

8
In four years, Suzy will be 20 + 4 = 24.

Then Mary will be 24 / 2 = 12.

Then Mary is now 12 - 4 = 8.

.

The final answer: 8