Part A you would just distribute your 3 to your X and your 5. After doing that you would get 3x+15+x=4x. Next you would combine like terms, meaning combine your x's together that is on the same side of your equal sign. So you would add 3x and x. When finished with that you would get, 4x+15=4x. You would then subtract your 4x on both sides of your equal sign. You then would get 15=0 which is no solution.
Part B you would distribute your 4 to your 1 and -x. After doing this your equation should then look like 4-4x=5x+8. Next you would try to get your like terms together. You would add 4x on both sides of your equal sign. Your equation should then look like 4=9x+8. Next you would subtract your 8 on both sides of the equal sign because your getting your terms together. Your equation should then look like, -4=9x. This answer would be one solution.
Part C you would combine your like terms, meaning add your 2x and x together to get your equation looking like, 3x+5=5+3x. You can tell just by looking at this equation it's going to be a infinite number of solutions.
9+7+8=24. The odds of getting a white marble is the greatest chance. I can't really figure out the percentage or decimal or whatever, but the least I can tell you is that it has a 9/24 or 3/8 chance.