The above will yield a triangle where leg 2 is the 1.5 hrs, leg 2 = 2 hrs and the hypotenuse is what you are trying to solve for.
Step 1: Draw a triangle, draw a line about an inch long then change your direction by the 10° and continue the line for another about inch and a quarter (trying to give some scale so that it all makes sense in the end). Now label the triangle as A (where you originally started the line) B (where you changed direction, & C where you completed the trip. Then label the sides opposite those angles the same letter only lower case a, b, & c.
Step 2: find the length of leg 1 (start point to correction point) ... 680 m/h x 1.5 h = 1020 m ... this is the first line.
Step 3: find the length of leg 2 (correction point to destination point) ... 680 m/h x 2 h = 1360 m ... this is the second line.
Step 4: we know that we changed course by 10°, if we had remained in a straight line then we know that is 180°, our angle will be equal to 180° - 10° = 170°
Step 5: lets use the la of cosines to solve this. If you labeled your triangle the same as I did mine then you should be looking at solving for side b using angle B and sides a & c. b2 = a2 + c2 - 2 x a x c x Cos B = 13602m +10202m - 2 x 1360m x 1020m x Cos (170) = b2 = 5622250.63m ... b = 2371.128556m
I would right it out in more steps if I were you so as to understand it better but I simply plugged it into a calculator.
Good luck Dalia