yes definately you can crack jee mains . The questions of jee mains are based on the conepts of ncert . So studying ncert will help you cover the syllabus of jee mains . Jee advance has a little different story . while the concepts are still from ncert , you need to practice lot more problems . Jee mains problems will be mostly ncert based . So once you have gone through ncert thoroughly , you will be able to solve the questions of jeee mains easily . After completing the ncert , start solving jee mains previous year questions .  It will help you understand the level of questions and will help you build your confidence