Answers:
10.
B: Austin did not combine -3 and -9 correctly.
11.
x=8.5
12.
2r-4s
13.
10x+3y
14.
k=2
Answer is <em><u>3</u></em><em><u> </u></em><em><u>m/</u></em><em><u>s.</u></em>
<h3>Step-by-step explanation:-</h3>
The ostrich ran at a constant velocity, so it's velocity was :

It is said that the bird ran for 160 seconds and it made it half-way to its nest, so the distance was :


And the velocity is :-


Therefore, the ostrich ran at a velocity of <em><u>3 m/</u><u>s</u> .</em>