Looked it up & the answer is -1.9
Answer:
x=17/2 y=1/6
Step-by-step explanation:
-1(x+3y=9)
1(x-3y=8)
_________
-x-3y=-9
x-3y=8
________
-6y/6=-1/6 y=1/6
x+3(1/6)=9
x+ 1/2=9
- 1/2 - 1/2
x=17/2
Step-by-step explanation:

As the x value increases by 1, the y value increases by 4. If the x value skips from 4 to 25, it increaes by 21. The y value can be found by multiplying 21 * 4 and adding the previous y value, 7. 21 * 4 is 84 and 84 + 7 = B) 91
Since a calculator is involved in finding the answer, it makes sense to me to use a calculator capable of adding vectors.
The airplane's ground speed is 158 mph, and its heading is 205.3°.
_____
A diagram can be helpful. You have enough information to determine two sides of a triangle and the angle between them. This makes using the Law of Cosines feasible for determining the resultant (r) of adding the two vectors.
.. r^2 = 165^2 +15^2 -2*165*15*cos(60°) = 24975
.. r = √24975 ≈ 158.03
Then the angle β between the plane's heading and its actual direction can be found from the Law of Sines
.. β = arcsin(15/158.03*sin(60°)) = 4.7°
Thus the actual direction of the airplane is 210° -4.7° = 205.3°.
The ground speed and course of the plane are 158 mph @ 205.3°.