To find the angle \( x \) in the triangle, we can apply the Law of Sines. According to the Law of Sines, the ratios of the lengths of the sides of a triangle to the sine of their opposite angles are equal:
\[ \frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C} \]
In the triangle described:
- Let \( A \) be the angle opposite the side of length \( 5.1 \) (angle \( x \)).
- Let \( B \) be the angle of \( 39^\circ \) opposite the side of length \( 3.3 \).
- Let \( C \) be the angle opposite the other side of length \( 3.3 \).
Using the Law of Sines, we set up the ratio for sides \( 5.1 \) and \( 3.3 \):
\[ \frac{5.1}{\sin x} = \frac{3.3}{\sin 39^\circ} \]
This can be rearranged to solve for \( \sin x \):
\[ \sin x = \frac{5.1 \cdot \sin 39^\circ}{3.3} \]
Next, we calculate \( \sin 39^\circ \):
\[ \sin 39^\circ \approx 0.6293 \]
Now substitute this value in:
\[ \sin x = \frac{5.1 \cdot 0.6293}{3.3} \]
Calculating the numerator:
\[ 5.1 \cdot 0.6293 \approx 3.2163 \]
Now compute \( \sin x \):
\[ \sin x = \frac{3.2163}{3.3} \approx 0.975 \]
To find \( x \), we now take the inverse sine:
\[ x \approx \sin^{-1}(0.975) \]
Calculating \( \sin^{-1}(0.975) \):
\[ x \approx 78.5^\circ \]
Thus, the value of \( x \) in the triangle is approximately
\[ \boxed{78.5^\circ} \]