To find the sum of the given arithmetic series, we can use the formula for the sum of an arithmetic series:

Sn = (n/2)(a1 + an)

where Sn is the sum of the series, n is the number of terms, a1 is the first term, and an is the last term.

In this case, the first term a1 is 2, the last term an is 50, and the common difference d is 2.

We can find the number of terms n by using the formula for the nth term of an arithmetic series:

an = a1 + (n-1)d

Substituting the values, we have:

50 = 2 + (n-1)(2)
50 = 2 + 2n - 2
50 = 2n
n = 25

Now we can substitute the values into the formula for the sum of the series:

Sn = (n/2)(a1 + an)
Sn = (25/2)(2 + 50)
Sn = (25/2)(52)
Sn = 25 * 26
Sn = 650

Therefore, the sum of the series 2-4+6-8+...+48-50 is 650.