Answer:
V = -9
Step-by-step explanation:
First, you get rid of the variable on one side of the equation. In this case, you'd pick -15V or -8V to add, because they're negative, to either side.
-15V - 40 = 23 -8V
+8V + 8V
The -8V and +8V cancel out, so you're left with -7V - 40 = 23.
Next, you'd add 40 to both sides to get rid of that number and leave yourself with a variable on one side and a regular number on the other side.
-7V - 40 = 23
+ 40 +40
You'll end up, after this step, at -7V = 63.
Finally, you divide both sides by -7 to get the variable alone.
-7V = 63
/-7 /-7
Now, you have what the variable is equal to.
V = -9