Explanation:
Okay, so...
The Median of a trapezoid is directly in the middle. For some weird mathimatical reason you won't ever need to know unless it's on an exam or you become a math major, its midsegment is the average of the top length and the bottom length.
In other words,
EF = ( BC + AD ) / 2
So for part 1, we can use that equation to find x.

![4x-18=[(x+12)+(3x-4)]/2](https://img.qammunity.org/2022/formulas/mathematics/high-school/8ynv8msh4v5s5l28rydi5sh9u23agkg14h.png)
- Simplify within parentheses.
![4x-18=[x+12+3x-4]/2](https://img.qammunity.org/2022/formulas/mathematics/high-school/s3isp5i23t5d94fso0qypraudcakx77mx6.png)
![4x-18=[x+3x+12-4]/2](https://img.qammunity.org/2022/formulas/mathematics/high-school/ygt58qddwxj3v6jjd94y2f7h3h44ou3k7u.png)
![4x-18=[4x+8]/2](https://img.qammunity.org/2022/formulas/mathematics/high-school/18ovjl2fig0ffyyk0hab9niz3r0tkku60i.png)




Part 2 is a lot easier now. All we have to do is plug in 11 for x.



-




-




Answer:
Part I: x = 11
Part II: