Answer:
21.4
Explanation:
We can solve for x using trigonometry 
Here are the Trigonometric Ratios
Remember SOH CAH TOA 
Sine = Opposite over Hypotenuse (SOH)
Cosine = Adjacent over Hypotenuse
Tangent = Opposite over Adjacent 
We are given the measure of ∠T ( 72° ) 
We are also given the adjacent side length (6.6) ( Adjacent = the side length that is not the hypotenuse nor the opposite side length ) 
And we need to find the hypotenuse ( longest side length )
We this information we can use the trigonometric ratio Cosine to solve for x
That being said we want to set up an equation 
(remember cosine = adjacent over hypotenuse ) 
 

Now we solve for x 
We can't get rid of the 6.6 itself so we want to multiply each side by x
now we have 

Step 2 divide each side by cos(72) 

We're left with x = 21.35804865
Finally we want to round to the nearest tenth of a foot and we get that x = 21.4