Question

Find each sum or difference mentally.- 30 +- 10- 10 +- 30- 30 - 1010 -- 30

Answer 1

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