Draw a sketch showing the aircraft at its first position due North of the VOR (360ºrdl). It is tracking 255º to its second position on the 330ºrdl. Consider the triangle made up by the aircraft's first position, the aircraft's second position and the VOR. The angles of this triangle are:
At the aircraft's first position: 255º - 180º = 75º
At the VOR: 360º - 330º = 30º
The third angle, at the aircraft's second position, is: 180º - (75º + 30º) = 75º.
This is an isosceles triangle and the two sides which are equal are the ones from the VOR to the aircraft's two positions.