x = 3
The equation should look like this:
5x + 2 = 17
Why 17? Because if you look at the opposite side of the parallelogram, you can see a parallel line that is the exact same length. Since it also isn’t an equation, we can tell this would be the true length of it.
Okay, to solve it, first subtract 2 on both sides of the equation. Why? Because on the left side of the equation (the numbers before the equal sign) we can see that there is one coefficient (number with a variable) and one constant (just a plain number). In equations like this, you want only coefficients or constants per side. To remove the constant from the left side, do the inverse of the number. Always remember that whatever you do on one side, has to be done to the other.
5x + 2 - 2 = 17 - 12
This equals:
5x = 15
Now, just divide by the coefficient, in this case 5, on both sides. This removes the 5.
5x/5 = 15/5
This leaves:
x = 3