We have here a right triangle. We can use trigonometric ratios (sine, cosine, or tangent) to find the length of any side of the triangle.
To do this, we can use angle 77 as a reference angle to find the side JK (the value of x, in this case.)
It is also important the largest side of a right triangle is the hypotenuse (JK).
Having this information, we can proceed as follows:
LJ = 6.9 feet
x = ?
We know that the opposite side to the angle 77 is the side LJ, and knowing this, we can use the sine ratio:
![\sin (77)=(opp)/(hyp)](https://img.qammunity.org/2023/formulas/mathematics/college/7k1mp2e9dtrg3k3a9atn902ho1ryg7e1lv.png)
Sine is the opposite side over the hypotenuse, then we have:
![\sin (77)=(6.9ft)/(x)](https://img.qammunity.org/2023/formulas/mathematics/college/yxmnxatp6rgojf32ypexq3e0xyf9nwpiwa.png)
Solving for x, we need to multiply the equation by x to both sides of the equation:
![x\cdot\sin (77)=(6.9ft)/(x)\cdot x\Rightarrow x\cdot\sin (77)=6.9ft\cdot(x)/(x)](https://img.qammunity.org/2023/formulas/mathematics/college/jn4qwxiy9984xs9ij28boriv09len8d6m1.png)
Since x/x = 1. We can now divide both sides of the equation by sin(77):
![x\cdot(\sin(77))/(\sin(77))=(6.9ft)/(\sin(77))\Rightarrow x=(6.9ft)/(\sin (77))](https://img.qammunity.org/2023/formulas/mathematics/college/k7clbzvytalvfdw3njr1w7b79wfiv6m9j2.png)
And the value for x (the side JK) is:
![x=(6.9ft)/(0.974370064785)\Rightarrow x=7.08149834377ft](https://img.qammunity.org/2023/formulas/mathematics/college/c6fe4n7dvi7pdzswasw235oa1pmy59uol8.png)
Rounding to the nearest tenth, we have that the value for x, the length of JK = 7.1 feet.