Answer:
x = 3.51
Explanation:
Since, formula to determine the area f a triangle is,
Area =

8 =

16 = x(3x - 7) + 1(3x - 7)
16 = 3x² - 7x + 3x - 7
16 = 3x² - 4x - 7
0 = 3x² - 4x - 23
3x²- 4x - 23 = 0
By quadratic formula,
x =

x =

x =

x =

x = 3.51, -2.18
But the length of sides can't be negative.
Therefore, x = 3.51 will be the answer.