I think you had a typo where interest should be 460 not 46 because even if the whole 6000 were invested at 7% he would have earned $420 in interest. Also if total investment was switched from 6000 to 600 the 46 in interest would work.
If the two angles of the triangle are equal. Well yes, because if the angles are both 50 degrees then the other angle will be 30. but it also depends on the shape of the triangle if they differ.
