A street hawker sells two types of newspapers one for Rs.25 and the other for Rs.40. If she sold 100 newspaper for Rs.2800. The newspapers she sold at Rs.25 are _____

Cost of one Newspaper=25
Cost of other Newspapers=40
X Newspaper Sold=25
Y Newspaper Sold=40
Total Sale
X + Y=100
Y=100-X
25X + 40Y= 2800
25X + 40 (100-X)=2800
25X + 4000- 40X=2800
-25X – 40 X=2800-4000
-15X=-1200
X=80