Answer:
9
Step-by-step explanation:
This is because 21/7 is 3. So, you use the scale factor of 3 to divide 27/3 to get x which is 9.
You can use a tangent:

We have opposite = 17 and adjacent = x.

substitute:
cross multiply
multiply both sides by √3

divide both sides by 3

Use the Pythagorean theorem:

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Other method.
triangle.
The sides are in the ratio 
Therefore

Part a : you could draw a line from each corner to the middle
This would give you 7 triangles in total
Part b : area of one triangle : 4.5*7.8 = 35.1 / 2 = 17.55in <-- area of 1 triangle
Part c : so if there are 7 triangles and the area of 1 triangle is 17.55, you would do:
7 * 17.55 = 122.85
Time Distance Distance / Time
2hrs 90 miles 90 miles / 2 hrs = 45 miles / hr
3hrs 135 miles 135 miles / 3 hrs = 45 miles / hr
5hrs 225 miles 225 miles / 5 hrs = 45 miles / hr
6hrs 270 miles 270 miles / 6 hrs = 45 miles / hr
Constant of proportionality is 45 miles / hr. This is the same for the four values. The unit rate is also 45 miles / hr.
Let us assume the Distance , d is directly proportional to Time, t
d α t
d = kt
Constant of proportionality is k which is D/T
d = 45t