How to break a long equation into multiple lines without numbering each row

[vmartel08]

This is related to How to achieve equivalent multline in LaTeX? and How to add fractional spacing in equation? with a few suggestions, including:

#set math.equation(numbering:"(1)")
$
  a + b + c + d + & e + f             \
        + med i + & j + k + l + m + n
$
$
  a + b + c + & d + e             \
        + med & f + i             \
        + med & j + k + l + m + n
$