From Mechanics

\displaystyle \begin{align} & \mathbf{F}1=37\textrm{.}6\mathbf{i}+13\textrm{.}7\mathbf{j}\ \text{N}\\ \end{align}

\displaystyle \begin{align} & \mathbf{F}2=43\textrm{.}3\mathbf{i}+25\mathbf{j} \ \text{N}\\ \end{align}

Resultant force= \displaystyle F1+F2=\left( 37\textrm{.}6+43\textrm{.}3 \right)\mathbf{i}+\left( 13\textrm{.}7-25 \right)\mathbf{j}=80\textrm{.}9\mathbf{i}-11\textrm{.}3\mathbf{j}\ \text{N}

This vector has magnitude \displaystyle \sqrt{{{80\textrm{.}9}^{2}}+{{\left( -11\textrm{.}3 \right)}^{2}}} \ \text{=81}\text{.7}\ \text{N}

using

\displaystyle {{F}^{2}}={{H}^{2}}+{{V}^{2}}

where

\displaystyle H=80\textrm{.}9\ \text{N},\ \ V=-11\textrm{.}3\ \text{N}