若x满足不等式组3

3各方同乘以-3得:
-21各方同+1得:
-20各方同除以2得:
-10所以:x+10>0
2x+8所以:2丨x+10丨-丨2x+8丨
=2(x+10)+(2x+8)
=2x+20+2x+8
=4x+28