First we take -1 and use arithmetic to make an equation which has -1 on both sides:
-1+6=7+2×(-1).
Now we replace -1 with x representing the variable x whose value we need to find:
x+6=7+2x.
To solve this, take away x from each side of the equation:
6=7+x.
Now we take 7 away from each side:
-1=x which is the same as x=-1.