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I do (my username is rabbit317)
the link to my username is https://artofproblemsolving.com/community/user/543359

Well I was in the leaderboard since June

Yep I did

Quarantine's  very boring

Angle(D) cuts off arc(ABC)   --->   angle(D)  =  ½·arc(ABC)

Angle(B) cuts off arc(ADC)   --->   angle(B)  =  ½·arc(ADC)  

Since arc(ABC) + arc(ADC) creates the whole circle:  arc(ABC) + arc(ADC)  =  360^o 

Therefore:  angle(D) + angle(B)  =  ½·arc(ABC) + ½·arc(ADC) 

                                                    =  ½·( arc(ABC) + arc(ADC) )

                                                    =   ½·( 360^o )  

                                                     =  180^o 

--->   (x + 24)^o + (x + 10)^o  =  180^o

--->                    2x^o + 34^o  =  180^o

--->                              2x^o  =  146^o

--->                                x^o  =  73^o 

Now, find the sizes of angle(A), angle(B), and angle(D).

Add these values together and subtract from 360^o to find the size of angle(C).

\(\frac{18^2\cdot \pi\cdot 140}{360}=126\times \pi\)

A 5 cm by 5 cm by 5 cm box contains 5 x 5 x 5 = 125 1-cm by 1-cm by 1-cm cubes.

None of the interior cubes touch the box  -  there are 4 x 4 x 4 = 64 interior cubes.

Also, none of the interior cubes on the top layer touch the box; there are 4 x 4 = 16 of these.

The total number that touch the cardboard is  125 - 64 - 16  =  45  1-cm by 1-cm by 1-cm cubes.

Geno, you're right! My bad :(

15 miles = 15 miles x ( 5280 feet / mile   =  79 200 feet

1 hour  =  1 hour x ( 60 minutes / hour ) x ( 60 seconds / minute )  =  3600 seconds

15 miles per hour  =  79 200 feet per 3600 seconds  =  22 feet per second

"per" means "divided by"

By similar triangles, the answer is 6*sqrt(2).

Complete square:

y = -x^2 - 4x = -(x + 4)^2 + 16

==> maximum value is 16

Complete the square:

3x^2 + 12x + 4 = 3(x + 6)^2 - 104

==> a = 3, h = -6, k = -104 

no, all the required information is provided in the question. I need helt figuring out what the side length of the sqare is

this "question" has been edited twice; it needs more editing 

EP answered that here 

if AB*

idk. they are hard. CalTheGreat, can you solve them?

You can track the probabilities using different case, i.e. Anty gets to 0 after 1 steps, 2 steps, 3 steps, and so on.  This gives us e_1 = 1/2*1 + 1/4*2 + 1/8*3 + 1/16*4 + ... By arithmetico-geometric series, e_1 = 2.  Similarly, e_2 = 1/2*2 + 1/4*3 + 1/8*4 + 1/16*5 + ... = 3, so (e_1,e_2) = (2,3).