You wrote;
"Hello I am Angelica. What are you?"
Therefore, just change
'너 뭐야?' to "<u>잘 지냈어요?</u>"
which means, "How are you?" or "How are you doing?"
Let maggie's age be x
brother's age = 2x +3
24= 2x +3 +x
21 = 3x
x = 7
It is the motto of the Marine Corps