Given that LX + 2L and ly + 7L are opposite to each other, find the value of - x + y

Given that LX + 2L and ly + 7L are opposite to each other, find the value of - x + y

∵ LX + 2L and ly + 7L are opposite numbers
∴ |x+2|+|y+7|=0
∵ |x+2|≥0,|y+7|≥0
∴ x+2=0,x=﹣2
y+7=0,y=﹣7
∴ ﹣x+y=2-7=﹣5.