Consider the following oxyanions:
`PO_(4)^(3-),P_(2)O_(6)^(4-),SO_(4)^(2-),MnO_(4)^(-),CrO_(4)^(2-),S_(2)O_(5)^(2-),S_(2)O_(7)^(2-)`
and find the value of R+Q-P
where P-number of oxy anions having three equivalent X-O bonds per central atom
Q=number of oxy anions having two equivalent X-O bonds per central atom.
R=Number of oxy anions having four equivalent X-O bonds per central atom.

Explanation

To solve the problem, we need to analyze each oxyanion and determine the number of equivalent X-O bonds for the central atom in each case. We will categorize them into three groups: those with three equivalent X-O bonds (P), those with two equivalent X-O bonds (Q), and those with four equivalent X-O bonds (R).

### Step 1: Identify the oxyanions and their structures
We have the following oxyanions:
1. \( PO_4^{3-} \)
2. \( P_2O_6^{4-} \)
3. \( SO_4^{2-} \)
4. \( MnO_4^{-} \)
5. \( CrO_4^{2-} \)
6. \( S_2O_5^{2-} \)
7. \( S_2O_7^{2-} \)

### Step 2: Analyze each oxyanion for equivalent bonds

1. **\( PO_4^{3-} \)**:
- Structure: One phosphorus atom bonded to four oxygen atoms (one double bond and three single bonds).
- Equivalent bonds: 4 (R).

2. **\( P_2O_6^{4-} \)**:
- Structure: Two phosphorus atoms, each bonded to three oxygen atoms (two double bonds and one single bond).
- Equivalent bonds: 3 (P).

3. **\( SO_4^{2-} \)**:
- Structure: One sulfur atom bonded to four oxygen atoms (one double bond and three single bonds).
- Equivalent bonds: 4 (R).

4. **\( MnO_4^{-} \)**:
- Structure: One manganese atom bonded to four oxygen atoms (one double bond and three single bonds).
- Equivalent bonds: 4 (R).

5. **\( CrO_4^{2-} \)**:
- Structure: One chromium atom bonded to four oxygen atoms (one double bond and three single bonds).
- Equivalent bonds: 4 (R).

6. **\( S_2O_5^{2-} \)**:
- Structure: Two sulfur atoms, with one sulfur bonded to three oxygen atoms (two double bonds and one single bond) and the other bonded to two oxygen atoms (one double bond and one single bond).
- Equivalent bonds: 3 (P) and 2 (Q).

7. **\( S_2O_7^{2-} \)**:
- Structure: Two sulfur atoms, each bonded to four oxygen atoms (two double bonds and two single bonds).
- Equivalent bonds: 4 (R).

### Step 3: Count the number of oxyanions for P, Q, and R
- **P (three equivalent X-O bonds)**:
- \( P_2O_6^{4-} \), \( S_2O_5^{2-} \) (1 from each sulfur), total = 3.

- **Q (two equivalent X-O bonds)**:
- \( S_2O_5^{2-} \) (1 from one sulfur), total = 1.

- **R (four equivalent X-O bonds)**:
- \( PO_4^{3-} \), \( SO_4^{2-} \), \( MnO_4^{-} \), \( CrO_4^{2-} \), \( S_2O_7^{2-} \), total = 5.

### Step 4: Calculate R + Q - P
Using the values we found:
- \( R = 5 \)
- \( Q = 1 \)
- \( P = 3 \)

Now, we can substitute these values into the expression:
\[ R + Q - P = 5 + 1 - 3 = 3 \]

### Final Answer
The value of \( R + Q - P \) is **3**.