2x - 2y = 2
2x - 2 x 0 = 2
2x - 0 = 2
2x = 2
x = 1
2x - 2y = 2
2 x 0 - 2y = 2
y = - 1
Answer:
The rate is 1.75 feet/seconds or 105 feet/minute.
Step-by-step explanation:
Given that,
Li walks at a constant rate of 7 feet in 4 seconds
To find the constant of proportionality, divide 7 feet by 4 seconds.
So,

1.75 ft/s is the constant of proportionality
We know that, 1 minute = 60 seconds
k = 105 feet/minute
So, the rate is 1.75 feet/seconds or 105 feet/minute.
Multiply both sides by three to get 2x=30
Then divide both sides by 2 to get x=15
The answer will be 40. As it doubles twice during 220mins- 10 to 20 and then 20 to 40.