**Given Information:**
In the given figure, DE is parallel to AC.

**To Find:**
We need to find the value of x in terms of a, b, and y.

**Solution:**

Let's analyze the given figure step by step.

1. **Identify the Corresponding Angles:**
Since DE is parallel to AC, we can identify the corresponding angles in the figure:
- Angle ECD is corresponding to angle DBA.
- Angle CDE is corresponding to angle BAD.

2. **Identify the Alternate Interior Angles:**
Since DE is parallel to AC, we can identify the alternate interior angles in the figure:
- Angle DCE is alternate interior to angle ABC.
- Angle CED is alternate interior to angle ABD.

3. **Identify the Co-interior Angles:**
Since DE is parallel to AC, we can identify the co-interior angles in the figure:
- Angle ECD is co-interior to angle DEC.
- Angle CDE is co-interior to angle CED.

4. **Use Corresponding Angles:**
Using corresponding angles, we can write the equations:
- ECD = DBA
- CDE = BAD

5. **Use Alternate Interior Angles:**
Using alternate interior angles, we can write the equations:
- DCE = ABC
- CED = ABD

6. **Use Co-interior Angles:**
Using co-interior angles, we can write the equations:
- ECD + CDE = 180°
- DEC + CED = 180°

7. **Combine the Equations:**
From the above equations, we can write:
- ECD + CDE = 180°
(ECD = DBA, CDE = BAD)
DBA + BAD = 180°

8. **Simplify the Equation:**
Since DBA + BAD is a straight angle, it is equal to 180°. Therefore, we can write:
- 180° = 180°

9. **Use the Value of y:**
Since we know that y = 180°, we can substitute this value into the equation:
- 180° = 180°

10. **Use the Value of x:**
Since DE is parallel to AC, and DEC + CED = 180°, we can substitute the value of y into the equation:
- DEC + CED = 180°
- x + y = 180°

11. **Simplify the Equation:**
Since we know that y = 180°, we can substitute this value into the equation:
- x + 180° = 180°

12. **Simplify Further:**
Subtracting 180° from both sides of the equation, we get:
- x = 0°

**Final Answer:**
Therefore, the value of x in terms of a, b, and y is 0°.

Where's the figure