LaTeX provides the commands that follow for use in math mode. 27 9 will display as 27 9. An operator is a function that is written as a word.
In the above example it is assumed by the LaTeX that each equation consists of two partspieces which are separated by an ampersand character.
Also that each equation is separated from the one before by an. However the latter kind of work often involves writing Math equations in digital form. For producing an inline expression the math expression should be written between the dollar sign. This is achieved by the use of two operating modes paragraph and math mode.