Resultant Vector using Components

A man pushing a toy car causes it to undergo 2 displacements. The first has a magnitude of 150 cm and makes an angle of 120degrees with the positive x axis. The resultant displacement has a magnitude of 140 cm and is directed at an angle of 35 degrees at the positive x axis. Find the magnitude and direction of the second displacement.



This was my failed try:



Displacement A + Displacement B = Displacement R

B = R - A



R = Rx + Ry

R = 140cos35i + 140sin35j



180° - 120° = 60

A = Ay + Ax

A = 150sin60j - 150cos60i (2nd Quad?? Not too sure if need to put negative here)



Hence:

B = Rx + Ry - (Ay + Ax)

B = 140cos35i + 140sin35j - (150sin60j - 150cos60i)

B = (140cos35 +150cos60)i + (140sin35 - 150sin60)j



B = sqrt( Bi^2 + Bj^2 )

B = 196



To find Direction

tetha = taninverse( (140sin35 - 150sin60)/ (140cos35 +150cos60) )

tetha = -14.65 degrees ?? weird??