Why does 768.5-13.402 equals 755.098?
Because it just is
\(\begin{array}{rlllllll}&7&6&8&.&5&0&0\\-&&1&3&.&4&0&2 \\-&-&-&-&-&-&-&-\\ &7&5&5&.&0&9&8\end{array}\)
