Problem:

Range A1:B5 contains numbers.
We want a total value of the cells occurring at the intersection of the following ranges:
1. Columns A:B, Row 2:2
2. Column A:A, Row 3:4
3. Columns A:B, Row 1:1 + Columns A:B, Row 5:5

Solution:

Use the SUM function as shown in the following formulas:
1. =SUM(A:B 2:2)
2. =SUM(A:A 3:4)
3. =SUM(A:B 1:1,5:5)