given an AP whose first term is 25 and the common difference is - 3

To find: the last term of a given AP

we know that the sum of AP is given by the formula

Solving we get

3n² - 53n + 232 = 0

n = 8 or

n cannot be a fraction hence we choose n as 8

Now for the finding number of terms, the formula is

solving we get the last term as 4