If i am given 10 math problems, and i can and do solve the first nine in the same way, i may struggle with the tenth problem if it requires a different method to solve it. this best illustrates the concept of

This best illustrates the concept of: Mental sets.

Explanation:

Mental sets refers to the tendency of solving problems using the same process that have worked before in similar issues. In some cases, it's necessary to use a different process in order to solve the problem correctly; this new process can be more elaborate or easier, nevertheless, the person is unable to use it because his mind is used to work in the same way all the time.