11. According to the Order of Operations, you start with the inner brackets and work outward. Then, finally, you do the sum left to right.
... 7 + (-10) +(4(5 -3))
... = 7 + (-10) +4(2)
... = 7 + (-10) + 8
... = -3 + 8
... = 5
12. (12 -10x) +3x -(2x +4x)
... = (12 -10x) +3x -6x . . . . . . combine terms inside parentheses
... = 12 - 10x + 3x - 6x . . . . . terms inside the left parentheses cannot be combined
... = 12 -7x -6x . . . . . . . . . . . here, we're combining terms left to right. Of course like terms can be added in any order you may desire, as long as you pay attention to signs. It is sometimes convenient to add all the positve terms, add all the negative terms, then find the sum of those. -10x +3x -6x = 3x -(10x +6x) = 3x -16x = -13x.
... = 12 -13x
