Given Information:
Ncr-1 = 56
Ncr = 28
Ncrr = 8

Explanation:
To find the value of r, we can use the formula for combinations (nCr), where n is the total number of items and r is the number of items chosen.

The formula for combinations is given by:

nCr = n! / (r!(n-r)!)

Where "!" represents the factorial of a number.

Step 1: Calculate the value of (n-1)Cr
Given: Ncr-1 = 56

We can rewrite this as:

(N-1)Cr = 56

Now, we can substitute this into the combinations formula:

(N-1)! / (r!(N-1-r)!) = 56

Since we don't know the value of N, we cannot solve this equation directly. We need more information.

Step 2: Calculate the value of Ncr
Given: Ncr = 28

We can rewrite this as:

N! / (r!(N-r)!) = 28

Step 3: Calculate the value of Ncrr
Given: Ncrr = 8

We can rewrite this as:

N! / (r!(N-r)(N-r-1)!) = 8

Step 4: Solving the equations
We have three equations (Step 1, Step 2, and Step 3) with three unknowns (N, r, and N-r). We can solve these equations simultaneously to find the value of r.

However, since the equations involve factorials, it is not feasible to solve them algebraically. We can use a trial-and-error method to find the values that satisfy all three equations.

Step 5: Trial-and-error
We can start by assuming different values for r and calculating the corresponding values of N using the equations from Step 1, Step 2, and Step 3.

For example, let's assume r = 2:

- Using the equation from Step 1: (N-1)C2 = 56
- Using the equation from Step 2: NC2 = 28
- Using the equation from Step 3: NC2(2-1) = 8

We can continue this process by assuming different values for r until we find the values that satisfy all three equations.

Final Answer:
The value of r cannot be determined from the given information. We need additional information or a different approach to solve the problem.