How do you solve #3x+7=31#?
With the exception of attempting to divide by zero, if you perform the same basic arithmetic operation (addition, subtraction, multiplication, division) to all terms on both sides of an equation using the same value, the equation remains valid.
We can subtract
and the new versions of equation are still valid.
Similarly, we can divide both sides of the last version by
and the result is still valid (again).