i'll help you w the first 3 so you can get an idea on how to do it and if you need more ask me.
1)
a + 5 = 9
a = 9 - 5 subtract both sides by 5
a = 4
2)
15 - c = 12
-c = 12 + 15 add both sides by 15
-c = -3
c = 3
3)
9 + 15 = y
24 = y
hope this helps, God bless!
