Hi there!
x = 20 is NOT a solution to this equation.
[tex] \frac{x}{2} = 40[/tex]
In this equation, when we want to find our value of x, we must multiply both sides of the equation by 2. In the current situation our variable x is divided by 2. Therefore, if we want to find its value, we must do the opposite of dividing, which is multiplying.
We end up with the following:
[tex] \frac{x}{2} \times 2 = 40 \times 2 \\ x = 80[/tex]
Therefore, the only solution to this equation is x = 80 and we can now conclude that x = 20 is NOT a solution to this equation.
~ Hope this helps you!
