Answer:
Step-by-step explanation:
f- -3u=21 divide each side by (-3)
-3u/-3=-21/3
u=-7
g) 23+a=12 use subtraction method , subtract 23 from both sides
23-23+a=12-23
a=-11
h) -9+b=15 use additional method, add 9 to both sides
-9+9+b=15+9
b=26
