Code 12 means the battery has been disconnected recently. Code 21 is an Oxygen Sensor code. Code 55 is fault code display completion code. Even though you have a code for the O2 sensor I would still get a proper diagnosis before you replace the sensor. Wiring and other factors can cause the code to set also.
12/21 is December 21. and December 21 is the winter solstice.
Stay As You Are was created on 1979-12-21.
D.D.D. was created on 2005-12-21.
WUTV was created on 1970-12-21.
How High was released on 12/21/2001.
12 is battery disconnencted recently 21 is oxygen sensor stays at center. 55 is end of message.
-43
55/21 = 213/21
12 : battery has been disconnected.55 : end of message.12 : battery has been disconnected.55 : end of message.
It is: 55*21 = 1155
21/55 = ~0.381818
the mean is 13.7
Mean (12, 18, 19, 20, 21) = 18
16, 12+15+21 = 48/3 = 16
It is 55 minus 21 = 34
12+9=21 21+15=36 36+13=49 49+6=55
If you mean 55/60 then it is 11/12