There are over 2500 RFC's. Each RFC is known by a number. For instance, RFC 1180 presents a tutorial on TCP/IP, RFC 1920 lists the current standards RFC's and explains the RFC standards process, and RFC 1941 is a FAQ list on the topic of Internet deployment in educational establishments.
MX record. A mail exchanger record (MX record) is a type of resource record in the Domain Name System that specifies a mail server responsible for accepting email messages on behalf of a recipient's domain, and a preference value used to prioritize mail delivery if multiple mail servers are available.
well y=mx+b is slope intercept form of a line. I dont see how these two equations are remotely similar. Also, in the slope intercept form, y=mx+b, m is equal to the slope. y2-y1/x2-x1 are the coordinates that you use to figure out the slope. B stands for the y-intercept.