Given:
- We have two vectors, a and b.
- The equation 3a + 2b = 7 is given.
- The ratio of b is x/2.

To find:
- The value of x.

Solution:

Step 1: Rearrange the equation 3a + 2b = 7 to isolate b.
- Subtract 3a from both sides: 2b = 7 - 3a.
- Divide both sides by 2: b = (7 - 3a)/2.

Step 2: Determine the ratio of b.
- The ratio of b is x/2, so we can write: b = (x/2)a.

Step 3: Equate the expressions for b from Step 1 and Step 2.
- (7 - 3a)/2 = (x/2)a.

Step 4: Solve for x.
- Multiply both sides by 2a to eliminate the denominators: 7 - 3a = xa.
- Rearrange the equation: xa + 3a = 7.
- Factor out a: a(x + 3) = 7.
- Divide both sides by (x + 3): a = 7/(x + 3).

Step 5: Determine the value of x.
- Substitute the expression for a from Step 4 into the equation: 3(7/(x + 3)) + 2b = 7.
- Simplify: 21/(x + 3) + 2b = 7.
- Subtract 21/(x + 3) from both sides: 2b = 7 - 21/(x + 3).
- Multiply both sides by (x + 3) to eliminate the denominator: 2b(x + 3) = 7(x + 3) - 21.
- Simplify: 2bx + 6b = 7x + 21 - 21.
- Combine like terms: 2bx + 6b = 7x.
- Rearrange the equation: 6b - 7x = -2bx.
- Divide both sides by -2x: (6b - 7x)/(-2x) = b.
- Simplify: (7x - 6b)/(2x) = b.

Conclusion:
The value of x is dependent on the expression (7x - 6b)/(2x) = b. The given equation does not provide enough information to determine the value of x.