Let the amount sold = \\(s\\) kg. Work backwards from what remains.<br><br>\\(\begin{aligned}<br>\text{After selling} &: 450 - s<br>\\<br>\text{Gave 20\% of remainder to neighbours} &: 0.20(450 - s) = 90 - 0.20s<br>\\<br>\text{Left} &= (450 - s) - (90 - 0.20s) = 360 - 0.80s<br>\\<br>360 - 0.80s &= 180<br>\\<br>0.80s &= 180<br>\\<br>s &= 225 \text{ kg}<br>\\<br>\text{Percentage sold} &= \frac{225}{450} \times 100\% = 50\%<br>\end{aligned}\\)<br><br>Final Answer: 50%