Answer:
The equation that represents the situation is x + 6 = 24
The value of x that makes the equation true is 18
Explanation:
Tim has x marbles,
Number of marble with Tim = x
The number of marbles Nirja has is 6 more than the number of marbles Tim has.
Number of marbles with Nirja = x + 6
Nirja has 24 marbles .
That is
 x + 6 = 24
 The equation that represents the situation is x + 6 = 24
On solving
 x = 24 - 6 = 18
 The value of x that makes the equation true is 18