Help needed : Unable to use CTRL+C or CTRL+D to copy formula

Hi all,

I am having an issue with pasting or dragging the formulas to other cells. If I used CTRL+D or Copy option in different cells values remains same as it is.

Example:
1. 5+5=10
2.5+6=10
3.5+7=10

Please can anyone help me to resolve this?

Thanks in advance!!!

Elango