https://github.com/jsquared21/Intro-to-Java-Programming/blob/1fcbde2319c24dd7065d26fbb366a44466ed0ecc/Exercise_03/Exercise_03_09/Exercise_03_09.java#L46 I think you should use `System.out.print("The ISBN-10 number is " + d1 + d2 + d3 + d4 + d5+ d6 + d7 + d8 + d9);`