1+x+x*2=3
First we need to find the x-value.
We can start by adding the like-terms:
x*2 => 2x
2x + 1 = 3
Now subtract 1 from both sides to attempt to isolate your variable.
2x -1 + 1 = 3-1
2x=2
and now to fully isolate the variable you divide by 2 or in other words multiply by 1/2 so that you can have your x variable alone.
2x/2 = 2/2
x=1
Now having your x value, all you have to do is plug it into the second equation and solve:
1-(1)-(1)2=
1-1-2=
1-3=
-2