[Tex/LaTex] Unused global options error for simple document class

warnings

I've already looked on stack exchange and found no clear answer that addresses my problem. I have an error "Unused global option(s): [10]." and after a modification "Unused global option(s): [letter,10]." I have no reason to believe an article can't use 10, 11 or 12 pt font, and I also want the page sizes to be U.S. letter which is why the letter option is there.

It was working completely fine, then randomly after some point I started getting this error when compiling. 

\documentclass[letter,10]{article}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{geometry}
\usepackage{graphicx}
\graphicspath{{Images}}

\title{test title}
\author{test name}
\date{September 20, 2017}

\begin{document}
\maketitle
\thispagestyle{empty}

\abstract{
test abstract
}

\end{document}

Best Answer

The article class options are letterpaper and 10pt not letter and 10, and actually both of these are the class defaults so you could just omit the optional argument, and use

\documentclass{article}

Note the unused option warning is a warning, not an error (TeX does not stop with an error message).

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