Add tags to equations in Pages
\tag is part of the amsmath LaTeX package rather than LaTeX itself. Pages doesn't support ams.

Internally, Pages uses blahtex to generate PNGs from the rudimentary maths environments. These individual equations don't have context of the page width, so it's not possible to add a correct amount of right spacing automatically within the equation environment.

However, Pages can do this. You can use the ruler to correctly center align the equation, and right align content outside of the equation.


Optional Create a new paragraph style for your equation lines. This preserves the ruler adjustments so you don't have to recreate this manually for each equation. Use the blue Update paragraph style button each time you make a change to the style to preserve the adjustment.


Create two tab stops:




Half width, center aligned. This becomes the center alignment for the equation.
Half width can be calculated by taking the 1 column width shown at the top of Layout (here, 17 cm) and dividing by 2 (here, 8.5 cm).
Full width, right aligned. This becomes the right alignment for the tag.





In a paragraph of your new equation paragraph style, press Tab. Insert your equation as normal. This will be center aligned on the page.
After your equation, press Tab. Insert the tag for the equation, which will be auto. right-aligned.