More practice with mark and lineup.
Modify "Example" so the + signs are lined up in
all of the equations, then type "ready".
x ~==~ a sub i ~ mark + ~ b sub i ~-~ c sub i
lineup + ~ d sub i - e sub i
lineup + ~ f sub i - g sub i
x ~==~ a sub i ~ + ~ b sub i ~-~ c sub i
#once neqn Ref | nroff >X1 &