Question

Forces of magnitude 3 Newtons, 5 Newtons and 7 Newtons act along the vectors (-3,-2,-9) (8,5,-9) (4,-1,-9)

Find the x component.

I have the answer at 4.968 however i can not arrive at it, attached is my working out. d has been used instead of c.

i have the x components as 2.531, -2.774 and -6.93 however these are not correct as they do not equal the answer of 4.968

Thanks