1) -30 +-10
plus sign multiplies minus sign to give a minus sign
=-30-10
= -40
2) -10+-30
plus sign multiplies minus sign to give a minus sign
= -10 -30
= -40
3) - 30 - 10
= - 40
4) 10--3
minus sign multiplies minus sign to give a plus sign
= 10 + 30
= 40
