To simplify 2-3(4x-1)-(7-x)3 you first perform mutiplication since there aren't parenthesis or exponent-->2-12x+3-21+3x, then combine like terms and you get -->-16-9x.

Multiply through the parentheses first- 2-(12x-3)-(21-3x). Then take everything out of parenthesis and don't forget two negatives make a positive- 2-12x+3-21+3x. Then combine like terms- -16-9x. Order of operations and remembering that subtracting a negative is like adding are the most important parts.