When two resistors of  $\left(800\pm 8\right)$ ohm and$$ $\left(600\pm 6\right)$  ohm are connected in parallel, value of the equivalent resistance is

$\frac{1}{R}=\frac{1}{R_1}+\frac{1}{R_2}\Rightarrow R=\frac{R_1{R}_2}{R_1+R_2}$

$R=\frac{800\times 600}{800+600}=\frac{480000}{1400}=343$ $\Omega$ 

$\frac{\Delta R}{R^2}=\frac{∆R_1}{{R_1}^2}+\frac{∆R_2}{{R_2}^2}$ 

$$\begin{gathered} \frac{∆R}{{\left(343\right)}^2}=\frac{8}{{\left(800\right)}^2}+\frac{6}{{\left(600\right)}^2} \\ ∆R=3.43 \\ \frac{∆R}{R}\times 100=\frac{3.43}{343}\times 100=1\% \end{gathered}$$

Equivalent resistance$=343\pm 1\%$