Question

complete the sentences . Had you joined coaching classes.......​

Answer 1

Here is your answer:

Had you joined coaching classes, you would have scored higher scores.

Explanation

It is a type of condition structure that means: 'If you had joined coaching classes, you would have scored higher grades.  

Example

Had you come earlier, you would have met him.

Had he studied harder, he would have topped the class.

Answer 2

Had you joined coaching classes, you could have scored better in the exams.

EXPLANATION:  

• The given sentence is incomplete and it is without a question mark which clearly states that an interrogative sentence cannot be formed with it.
• So, we can make it a conditional sentence, which presents a condition about things that may or may not have occurred had the person has fulfilled the given condition.
• Here, the speaker says that had the person joined the coaching classes then he could have been able to score good grades in his exam.