Please help!!!!

Question

Flying against the wind, an airplane travels 7680

 kilometers in 8

 hours. Flying with the wind, the same plane travels 5360

 kilometers in 4

 hours. What is the rate of the plane in still air and what is the rate of the wind?

Answer 1

You have 2 unknowns for this problem, so you need 2 equations. The basic equation you have to know is D=rt (Distance = rate x time)

Let x=speed in still air

Let y= wind speed

Against the wind: 7680=(x-y)8 (It is subtraction because the plane will go slower against the wind)

Simplifies to 7680=8x-8y

With the wind: 5360=(x+y)4 (The wind helps the plane go faster, so this equation is addition)

Simplifies to 5360=4x+4y

Can you solve these equations by substitution or addition methods? Either one will work. I would probably multiply the 2nd equation by 2 and use the addition method to eliminate the y and solve for x.