Hope this helps :) If you have a doubt just comment :)
Answer:
Step-by-step explanation:
-4 is really -1 * 4
-4² = -1 * 4²
-4² = -1 * 16
-4² = -16
Use parenthesis to square
(-1 * 4)² = (-4)²
(-4)² = 16
We can observe that the function describing the graph is linear and so the equation is of linear nature:

Numbers m and n have special names. m is called the slope, n is called y-intercept.
From the graph one can tell that the line intercepts y-axis at y = -1 that means n = -1. What about the slope you say?
The slope can be calculated using two points' coordinates that lie on the line:

Now our line has an equation,

Hope this helps.
Distance to travel = 20 m.
Let us determine the time, t, that each participant took to complete 20 m.
Barbara:
Average speed = (3 m)/(2 s) = 1.5 m/s
t = 20/1.5 = 13.3 s
Mark:
t = 5 s
Carlos:
y = x + 1
where
y = 20 m
x = time, t
Therefore
t =x = y - 1 = 20 - 1 = 19 s
Summary:
Barbara: 13.3 s
Mark: 5 s
Carlos: 19 s
Answer:
The winner is Mark
x+3<8
8-3 =5
X<5
any number less than 5 will work