x大于7时,化简为x+5+x-7+x+10=3x+8 x小于等于7大于-5时,化简为x+5-x+7+x+10=x+22 x小于等于-5大于-10时,化简为-x-5-x+7+x+10=-x+12 x小于等于-10时,化简为-x-5-x+7-x-10=-3x-8