Area of the big cardboard = 25 × 25 = 625 cm&sup2;.<br><br>
The cut-away square has side 17 cm (from the figure).<br>
&bull; Area of cut-away square = 17 × 17 = 289 cm&sup2;.<br>
&bull; Remaining area = 625 − 289 = 336 cm&sup2;.<br><br>
Final Answer: 336 cm&sup2;