1st) You can read the 1st article in 7 ways
2d) You can read the 2nd article in 6 ways (because 1 is already chosen)
3rd) You can read the 3rd article in 5 ways (because 2 are already chosen)
4th) You can read the 4th article in 4ways (because 3 are already chosen)
5th) You can read the 5th article in 3 ways (because 4 are already chosen)
Total ways = 7x6x5x4x3 = 2520 ways
You can also find te solution in using the permutation formula
₇P₅ = (7!)/[(7-5)!] = 2520 ways