What is 301931 rounded to the nearest 100,000

Is δ pmr similar to δ smn ? if so, which postulate or theorem proves these two triangles are similar?

F(n + 1) = f(n) – 8. if f(1) = 100, what is f(6)?

Offering 30 if a plus b plus c equals 68 and ab plus bc plus ca equals 1121, where a, b, and c are all prime numbers, find the value of abc. the answer is 1978 but i need an explanation on how to get that.