Synthetic examples for manual entry; not a CSV or workbook.
B2=5; C2=3 (numeric inputs).
Broken: =2(3+4)
Corrected: =2*(3+4) -> 14
Multiplication: =B2*C2 -> 15
Two-argument sum with semicolon setting: =SUM(B2;C2) -> 8
Comma-setting counterpart: =SUM(B2,C2) -> 8
Change B2 to 6: multiplication 18, sum 9.