a) 2(3x+7)-5(2x+1)=3(-2x+3)-7(2x+1)+5
6x+14-10x-5=-6x+9-14x-7+5
-4x+9=-20x+7
16x=-2
x=-1:8
b) -2(2x-5)+6(3x+1)+25=2(2x+3)-5(-x+7)
-4X+10+18X+6+25=4X+6+5X-35
14X-9X=-41+6-35
5X=-70
X=-14
c) x+2x+...+100x=5+10+...+500
x=5
d) 23(2x-5)+41(3x+7)-115=-20(x+11)+15(4x+7)+43
46x-115+123x+287-115=-20x-220+60x+105+43
169x-40x=148-220-287+230
129x=-129
x=-1
