aruindo to read my xbee accelerometer data

okay thanks but how can i fix it

byte[(12)*256]+(13)] = Serial.read( ,x);

in this i mean that my 12th and 13th byte are my x value in my packet fram ,

[(12)*256]+(13)] this is because i have MSB , LSB to be added together for my ADC .

can you help please ?
thanks