Why does this line not work?

while(numb123 > 3000 && < 9000) {

I assume it needs to be:

while ((numb123 > 3000) && (numb123 < 9000))

The compiler can’t read your mind.

Relational operators are binary operators and require two operands to work. Your second expression only has one operand.

NMetallic:
while(numb123 > 3000 && < 9000) {

try
while (3000 < numb123 < 9000)

filk:
try
while (3000 < numb123 < 9000)

No, don’t; it’s a really bad idea.