Answer:
=SUM(C2:C4, C7)
Explanation:
In excel 'C' represent the cell ( intersection of row and column ),
Also, '=sum( )' represents the function of addition in the excel,
Also, when we operate all consecutive cells from
to

Then under the function formula we write

And, when we operate a cell
with non consecutive cell

Then under the function formula we write

Hence, C2+C3+C4+C7 can be written as,
=SUM(C2:C4, C7)