Hello there!
First, let's understand what we are dealing with here.
8a + 7 = 31
Our goal is to isolate 8a and then solve for a.
Since 8a is being added by 7, we need to cancel it out. The only way to do that is to perform the opposite order of operations to +7.
The opposite order of operations of +7 is -7, so subtract 7 from both sides of the equation.
7 - 7 = 0
31 - 7 = 24
We now have:
8a = 24
Now we need to solve for a. However, it is being multiplied by 8, so we need to perform the opposite order of operations once again to solve for a.
Divide both sides by 8 to solve for a.
8a / 8 = a
24 / 8 = 3
A = 3 is your solution.
I hope this helps!