Here, the first number is 11, which when divided by 4 leave remainder 3 between 10 and 300. Last term before 300 is 299, which when divided by 4 leave remainder 3.
∴ nth term, an = a + (n - 1)d = 299
⇒ 299 = 11 + (n - 1)4
⇒ 299 - 11 = (n - 1)4
⇒ 4(n - 1) = 288
⇒ (n - 1) = 72
∴ n = 73