First we write the kinematics equations:
a
v = a * t + vo
r = a * (t ^ 2/2) + vo * t + ro
For Wanda we have: a = 0
v = 5
r = 5 * t
For Dave we have: v = 10
r = 10 * (t-120)
To solve the system of equations, we graph both functions and see where
they intersect.
We have to intersect in the ordered pair:
(t, r) = (240, 1200)
answer If they continue walking at these rates, Dave catch up to Wanda in 240s (1200 ft)
Hi Andres,
----------------------------------------
Coordinates:
(6,12) and (3,21)
----------------------------------------
Slope:
Formula: 
Solution: 
Slope: -3
----------------------------------------
Compute the y intercept:
Use: y = mx + b
y = (-3)x + b
12 = (-3) x 6 + b
----------------------------------------
Isolate b:
(-3) x 6 + b = 12
-3 x 6 + b = 12
-18 + b = 12
b = 30
----------------------------------------
Slope Intercept Form:
Follow y = mx + b
m = slope
b = y intercept
Answer: y = -3x + 30
----------------------------------------
Point Intercept Form:
Formula: y - y1 = m(x - x1)
m = slope
y1 and x1 = first coordinate set.
m = -3
y1 = 12
x1 = 6
Answer: y - 12 = -3(x - 6)
----------------------------------------
Part B:
Approximately for every day he spends delivering he spends a 2.1 minutes on it per day. Well, the reason I say this is because on the chart it says he spends 10 days. When you multiply 10 and 2.1 you get 21!
----------------------------------------
Hope This Helps :)