The car's velocity after 5s : 10 m/s
<h3>Further explanation</h3>
Given
velocity=v=72 km/h=20 m/s
time=t = 5 s
acceleration=a = -2 m/s²
Required
velocity after 5s
Solution
Straight motion changes with constant acceleration

vf=final velocity
vi = initial velocity
Input the value :

The car is decelerating (acceleration is negative) so that its speed decreases
Answer: 368 grams of sodium reacted.
Explanation:
The balanced reaction is :

According to stoichiometry :
2 moles of
are formed from = 2 moles of 
Thus 16 moles of
are formed from=
of 
Mass of 
Thus 368 grams of sodium reacted.
So, the answer to 27.) would be <em>2x.</em> Both 6x and 2x can be divided by 2x, but they can't go any higher without the end-answer becoming a fraction. As such, 2x is the greatest common factor.
For 28.), x and x^2 can't be like terms, since like terms have the same variable and exponent :)
Hope I could help!