Answer:
The longest side length is 31.764705882352941
Explanation:
Add up all the sides and then make it equal to 102
To get perimeter you add up all the sides
(12a) + (6a + 8) + (6a + 8) + (10a - 4) = 102
(18a +8) + (16a + 4) = 102
34a + 12 = 102
- 12 - 12
34a = 90

a = 2.647058823529412
Then plug in a to 12a to get the longest side length
12(2.647058823529412) = 31.764705882352941