Lines a and b are intersected by lines l and m. Angles formed by the intersections of the lines are listed from left to right and top to bottom. Lines a and l: angles 1, 2, 4, and 3. Lines b and l: angles 5, 6, 8, and 7. Lines a and m: angles 9, 10, 12, and 11. Lines b and m: angles 13, 14, 16, and 15.