Final answer:
To find the value of x, we set up an equation using the sum of the marks and frequencies. Simplifying the equation gives us x = 7.
Step-by-step explanation:
To find the value of x, we need to calculate the sum of the marks and frequencies. The sum of the marks is 3 + 4 + 5 + 6 + 7 + 8 = 33. The sum of the frequencies is 5 + (x-1) + x + 9 + 4 = 19 + 2x. Since the mean mark is 5, we can set up the equation (33 + 19 + 2x) / (6 + x) = 5.
Simplifying the equation gives us 52 + 2x = 30 + 5x. Subtracting 2x from both sides gives us 52 = 30 + 3x. Subtracting 30 from both sides gives us 22 = 3x. Dividing both sides by 3 gives us x = 7. Therefore, the value of x is 7.