To find the % error of the enthalpy of the reaction we have to use the following formula:
[tex]\%error=\frac{|theoreticalvalue-experimentalvalue|}{theoreticalvalue}\cdot100[/tex]Replace for the given values and solve:
[tex]\begin{gathered} \%error=\frac{|92kJ-38kJ|}{92kJ}\cdot100 \\ \%error=\frac{|54kJ|}{92kJ}\cdot100 \\ \%error=0.59\cdot100 \\ \%error=59 \end{gathered}[/tex]The %error is 59.