Directed Numbers

Rules for multiplication
 * +x+=+
 * A positive by a positive is a positive
 * Eg 3x5=15
 * +x-=-
 * A positive by a negative is a negative
 * Eg 3x-5=-15
 * -x+=-
 * A negative by a positive is a negative
 * -3x5=-15
 * -x-=+
 * A negative by a negative is a positive
 * -3x-5=15