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The sixth "Learning Cup" national mathematics knowledge application competition, grade eight (B) examination paper.
Where is the map of 12?

13.

(1) solution: let the increased area be x.

The ratio of window area to building area is 10%

∴ The increase rate is10+x/100+x.

∴ 10+x/ 100+x- 10/ 100

=90X/( 1000+ 10X)

∵X & gt; 0

∴90x>; 0 1000+ 10X & gt; 0

∴ 90X/( 1000+ 10X)>0