The given AP is 3, 8, 13,..., 253.
Let us re-write the given AP in reverse order i.e. 253, 248, .., 13, 8, 3.
Now, the 20th term from the end of the given AP is equal to the 20th term from beginning of the AP 253, 248,., 13, 8, 3.
Consider the AP 253, 248,….. 13, 8, 3
Thus, the 20th term from the end of the given AP is 158.