Question 975828
This one I did yesterday.

x= the standard version
y=the 4.9 version 
x+y=710 
2.5x + 4.9 y=2279 
multiply first by (-2.5)
-2.5x-2.5y = -1775;; Now add the first and the second to eliminate x. 
2.4 y=504;;; divide both sides by 2.4
y=210 of the 4.9 MB
x=500 of the 2.5 MB 
Check
210*4.9=1029
500*2.5=1250
Total is 2279 , all units are MB