Find direction from three displacement vectors?

[amhasque]

Consider the three displacement vectors A with arrow = (-4i hat bold − 3j hat bold) m, B with arrow = (6i hat bold − 8j hat bold) m, and C with arrow = (-3i hat bold + 5j hat bold) m. Use the component method to determine the following.

(a) The magnitude and direction of the vector D arrowbold = A with arrow + B with arrow + C with arrow.
magnitude = 6.09m

direction = ___ I came up with 279 degrees but WebAssign said this was the wrong answer - ( tan-1(6/-1) = -80.5 + 360 = 279 degrees )
-Please let me know what I did wrong. Thanks in advanced!

https://s.yimg.com/hd/answers/i/e9b78a68cdc740ec9325bef84b8802c5_A.jpeg?a=answers&mr=0&x=1411359677&s=c34e6240b312c8a385b3b438af3f4519

 

[Simon Bridge]

Show your working - I think you have misplaced a minus sign.