145 + x = 3x + 45
you want to get all the x's onto one side; you can do this by subtracting 1x from both sides of the equation:
145 + x = 3x + 45
-x -x
Now you are left with:
145 = 2x + 45
you want to have all the numbers without the x variable on the other side to solve for x; you can do this by subtracting 45 from both sides of the equation to isolate 3x:
145 = 2x + 45
-45 -45
Now you have:
100 = 2x
divide both sides by 2 to solve for x
100/2 = 50
Final answer: x = 50