LuckyDucky

She walked 1 km to school and 1 km back home, her total distance is 1+1=2 km.

She spent 30 minutes walking to school and 10 minutes walking back home, her total time is 30+10=40 minutes = \(\frac{40}{60}=\frac{2}{3} hours\)

Therefore her average speed in km is $\(\frac{2}{\frac{2}{3}}=\boxed{\mathrm{(A)}\ 3}\)

N = 16.

So, 16 positive integer solutions are possible for this equation.

Is this from AOPs?

100000000% agree!

This image is excellent I recommend to view it!

https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.onlinemath4all.com%2Fgemdas-order-of-operations.html&psig=AOvVaw3v8y-v4md6S_WjSpIc2j7Q&ust=1588636312946000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCODHq8vxmOkCFQAAAAAdAAAAABAD

Ok here's my solution, 

\(\begin{align*} (-2)^4 &= (-2)(-2)(-2)(-2) = 16,\\ 2^4 &= 2\cdot 2\cdot 2\cdot 2 = 16,\\ (-3)^3&= (-3)(-3)(-3) = (9)(-3) = -27,\\ 3^3 &= 3\cdot3\cdot3 = 27, \end{align*}\)

\((-2)^4 -2^4 + (-3)^3 - 3^3 = 16-16 -27-27 = \boxed{-54}.]\)

So the thing to take away in this question is to always remember that in solving these questions the order of operations in KEY!!!

Oh thats cool! 

But like don't you have a job and stuff?

I noticed that to LOL!

Then the final answer is 168/6 * 6/35 = 1008/210

= 24/5