Explanation:
I guess, our job is to find out the number to put into the blue dot, so that the squadron is true.
that is called solving the equation.
and the blue dot is a "variable". let's call it x.
so,
x/2 - 7 = 17
now, by making the same transformations on both sides of the "=" sign we don't change the meaning of the equation. we just make it clearer to understand.
so, for example, we can add 7 to both sides.
and we get
x/2 = 24
aha !
now only the fraction is a little bit disturbing.
so, let's multiply both sides by 2.
and we get
x = 48
and there is our answer.
if and only if we put "48" as number into the blue dot, the equation is true. for any other value it is false.