First, multiply the 2 times (x-5) and you get 2x-10 on the left side.
Then on the right side, add up all the similar terms and you get 30 (the -3x and +3x cancel each other out.
2x-10=30
Then add 10 to both sides and you get 2x=40.
Then divide both sides by 2 and you get x=20.
Answer is B.