Helpppp ASAPS i need your help i give brainlist to the correct answer only 2 and 3

Answer:
see
Step-by-step explanation:
1.
AD²+BD²=AB²
AD²+12²=15²
AD²+144=225
AD²=225-144
AD²=81
AD=√81
AD=9
2.
AC=AD+DC
AC=9+16
AC=25
3. I don't know what's the answer here.
Please give me brainlist.