Write the thing spaced out:
4a -5b +6ab -8b -3a
The signs (+,-) are assigned to the numbers it is in front of.
We minus the "like" terms:
4a - 3a = 1a
-5b - 8b = -13b
+6ab = +6ab
Put them all together:
1a - 13b + 6ab
The answer for, "4a - 5b + 6ab - 8b - 3a" = "1a - 13b + 6ab"
