<PRE><B>Question 820173</B>
head start:
s = d / t
d = s * t
d = 40 / (11 - 9)
d = 20 miles
---
when the trucks meet they will both be distance D from the yard
---
first truck:
D = 40(t + 2)
---
second truck:
D = 50t
---
D = 40(t + 2) = 50t
40t + 80 = 50t
10t = 80
---
t = 8
---
answer:
the trucks will meet at: 
11 + 8
19:00 or 7:00 PM
---
Solve and graph linear equations:
https://sooeet.com/math/linear-equation-solver.php
---
Solve quadratic equations, quadratic formula:
https://sooeet.com/math/quadratic-formula-solver.php
---
Solve systems of linear equations up to 6-equations 6-variables:
https://sooeet.com/math/system-of-linear-equations-solver.php</PRE>