<span>1. h = -16t² + vt + c
⇒ vt = 16t² + h - c
⇒ v = 16t + (h-c)/t
2. c = 5 ft
t = 3s
h = 131 ft
v = 16*3 + (131-5)/3 = 48 + 42 = 90 ft/s
when t=0, velocity is not defined. That means at t=0, there is no velocity of the t-shirt or it is 0.
</span>
Answer:

Step-by-step explanation:
Let c represents child bikes and a represents adult bikes.
Given : Each child bike requires 4 hours to build and 4 hours to test. Each adult bike requires 6 hours to build and 4 hours to test.
With the number of workers, the company is able to have up to 120 hours of building time and 100 hours of testing time for a week.
Then, the required system of inequality :-

If company make 10 child bikes and 12 adult bikes in the week.
Then Put c=10 and a=12 bikes in (1) and (2).
⇒Bike order meets the restrictions
⇒Bike order meets the restrictions
Hence, the system of inequality best explains whether the company can build 10 child bikes and 12 adult bikes in the week.

It cannot be 30, because the sum of two sides should be more than third side
-not D
10+18=28 <30
it cannot be 6 +10 < 18
it cannot 8
8+10=18
so it is has to be C) 12
12+18>10
10+12>18
10+18>12
answer C. 12 cm