A. Directions: Solve the system of equations (by elimination) 1.
x + 2y = 7
x - y = 4

​

x=5

Step-by-step explanation:

X+2y=7

X-y=4

2(x-y)= (4)2= 2x-2y= 8

x+2y=7

2x-2y=8

3x=15

15/3=5   X=5

-2y+2y=0

x + 2y = 7(1)

x - y = 4 (2)

Step-by-step explanation:

subtracting equation 2 from 1

x+2y=7

x-y=4

-

2y--y=7-4

3y=3

y=3/3=1

multiplying equation 2 by 2

2x-2y=8(3)

adding equation 1 and 3

2x-2y=8

x+2y=7

+

2x+x=8+7

3x=15

x=15/3=5

:.x=5

:.y=1

since the airplane is moving with constant speed then the distance travelled can be calculated by x=u*t

in km/h would be:

x=640*3.5=2.240 km

in m/s would be:

u=640 km/h= 640.000 m/h =640.000/ 3600 m/s =177.8 m/s

t= 3.5 h= 3.5 * 3600 s=12.600 s

then x=u*t= 177.8*12.600= 2.240.280 m