Katie said,”negative numbers are integers.” what was her error?

Two angles are complementary. the larger angle is 36 more than the smaller angle. what is the measure of the larger angle?

Suppose you are choosing a 6-digit personal access code. this code is made up of 4 digits chosen from 1 to 9, followed by 2 letters chosen from a to z. any of these digits or letters can be repeated. find the total number of personal access codes that can be formed. 492,804 341,172 39,917,124 4,435,236

Need solving this 2nd limit problem.