math symbolsUse real symbols, not alphabetic characters

If you need math sym­bols in­fre­quently—some light ad­di­tion and sub­trac­tion, the oc­ca­sional neg­a­tive num­ber—you can get by with­out spe­cial sym­bols. Use the plus sign (+) and equals sign (=) as usual. Use the en dash as a mi­nus sign () (see hy­phens and dashes).

If you need to do mul­ti­pli­ca­tion or be­yond, in­sert real math sym­bols by hand.

123 x 345 - 678 = 41757wrong
123 × 345 − 678 = 41757right
How to insert math symbols

Word InsertSymbols panel → SymbolMore Symbols

OS X Word 2011 InsertSymbolAdvanced Symbol

OS X Word 2016 Insert menu → Advanced Symbol

Pages EditEmoji & Symbols (or con­trol + ⌘ + space). In the re­sult­ing char­ac­ter palette, if you don’t see a list of sym­bol cat­e­gories on the left, change the view by scrolling to the top of the palette and click­ing the but­ton in the up­per right. From the list on the left, se­lect Math Symbols. Dou­ble-click the sym­bol you want. (Spe­cial han­dling is needed for foot and inch marks.)

HTML Mi­nus sign is &mi­nus; mul­ti­pli­ca­tion sign is × di­vi­sion sign is &di­vide; (many oth­ers are also supported)

by the way
  • The mul­ti­pli­ca­tion sym­bol is also prop­erly part of di­men­sional notations.

    8.5″ x 14″wrong
    8.5″ × 14″right