Please help! I will mark as brilliant for true right answers!! Thanks.

Answer:
21) n= -13 so replace the n with -13. you do 18- -13 which is 31
22) 9.45
23) -2.2
Answer:
21. 31.
22. 9.45
23. -2 1/5.
Step-by-step explanation:
18 - (-13)
= 18 + 13
= 31.