\documentclass[12pt,letterpaper]{paper}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%DATOS DE LA GUIA
\newcommand{\curso}{{Módulo}}
\newcommand{\carrera}{{Carrera}}
\newcommand{\temas}{{\ldots}}
\newcommand{\guia}{Guía Nº X}
\newcommand{\unidad}{Unidad XX}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%Useful Packages
\usepackage{amssymb,amsmath,amsthm,hyperref,mathtools,bbm,cancel,multicol,enumitem,tabularx,fancyhdr,booktabs,pdflscape}
%language
\usepackage[utf8]{inputenc}
\usepackage[spanish,activeacute]{babel}
%better fonts
\usepackage[T1]{fontenc}
\usepackage{microtype}

%margins
\usepackage[top=35mm,left=15mm, right=15mm, left=15mm, headheight=20mm, headsep=10mm]{geometry}

\begin{document}

\pagestyle{fancy}
%... then configure it.
\fancyhead{} % clear all header fields
\fancyhead[L]{\includegraphics[width=1.5in]{logoINSTMAT.jpg}}
\fancyhead[R]{
	\hfill{\large\textbf{\curso}}\\
	\hfill{\large\textbf{\carrera}}\\
	}
\fancyfoot{} % clear all footer fields


\begin{center}
	{\LARGE \textbf{\guia\ - \unidad}}\\
	Temas: \temas.  \\[1.0cm]
\end{center}


\begin{enumerate}
	\item 
\end{enumerate}

\newpage
\begin{center}
	{\large \textbf{Respuesta a ejercicios seleccionados}}
\end{center}

\end{document}