add or subtract the following directed number
(-105)+ ( -117)
(-168)+(-35)
(+310)+(+130)
(+217)-(-128)
(-246)-(+14)
(-129)-(-116)
(+63)+(-127)+(-18)
(-21)+(+14)+(-42
Solution:
Using: (+a) + (+b) = a + b,
(-a) + (+b) = - a + b,
(+a) + (-b) = a - b
Using: (+a) + (+b) = a + b,
(-a) + (+b) = - a + b,
(+a) + (-b) = a - b
(-a) + (-b) = - a - b
- (-168)+(-35) = -168 - 35 = -203
- (+310)+(+130) = 310 + 130 = 440
- (+217)-(-128) = 217 + 128 = 345
- (-246)-(+14) = - 246 - 14 = -260
- (-129)-(-116) = - 129 + 116 = -13
- (+63)+(-127)+(-18) = 63 - 127 - 18 = - 82
- (-21)+(+14)+(-42) = -21 + 14 - 42 = -7 - 42 = - 49