Answer:
See below.
Step-by-step explanation:
Well first, we need to find the weight of the table. We know that 8 boxes weighs a total of 240kg (since each box weights 30kg). Thus, we can conclude that the table weighs 70kg by doing 310-240=70.
Now, we can write our function. Let 
equal the amount of boxes.
The table is a set weight, so that would be our constant.
Thus, we will have:
30x represents the weight each box of book adds to the total. One box equals 30kg, 2 boxes equal 60kg, etc.
The 70 represents the unchanging weight of the table.
In terms of W(x), it will be:
Answer:
3
Step-by-step explanation:
9 divide by 3 is 3 itself so the answer is 3
I don't understand what you mean by 300 and 70, unless you meant 300/70 (in that case it would be 30/7).
5/10 would be 1/5
8/100 would be 2/25.
As usual, draw a diagram. You can easily see that if you are x away from the wall,
<span>the angle of elevation of the bottom of the screen (A) is </span>
<span>cotA = x/3 </span>
<span>A = arccot(x/3) </span>
<span>angle B to the top is </span>
<span>cotB = x/10 </span>
<span>B = arccot(x/10) </span>
<span>So, since θ = B-A </span>
<span>dθ/dt = dB/dt - dA/dt </span>
<span>= -3/(x^2+9) + 10/(x^2+100) </span>
<span>= 7(x^2-30)/((x^2+9)(x^2+100)) </span>
<span>so, at x=30 </span>
<span>dθ/dt = 203/30300</span>
