x-5(3x+4)-3x=-146 can be simplified: x-15x-20-3x=-146⇒-17x-20=-146. You can get rid of all the negatives by multiplying right through by -1: 17x+20=146, so 17x=126 from which x=126/17=7 and 7/17. That doesn't look like a friendly answer. If the question was: -5(3x+4)-3x=-146 then -15x-20-3x=-146. That simplifies to -18x-20=-146. Multiplying throughout by -1 changes all the negatives to positives: 18x+20=146, so subtracting 20 from each side: 18x=126 and x=126/18=7. That's much friendlier! To check it out put x=7 in the original equation: -5*25-21=-146. Checks out!