Hi dear,
You have to score more than 50 percent in your 12th. This is only eligibility for taking admission in JMI. There is no age restrictions. For important dates you can check here
https://www.google.co.in/url?q=https://www.careers360.com/exams/jmi-entrance-exam&sa=U&ved=2ahUKEwiA4eTjvIPoAhXg4jgGHee3AYkQFjAQegQIAhAB&usg=AOvVaw13Zk6vohvUlJv2OR-orwDa
Hope it helps.
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