CPhill

The total change in temperature was l -10 l + l 18 l = 10 + 18 = 28 degrees

The relative change was -10 + 18   = 8 degrees

I assume this might be...

576=[3/4 ]r^2      multiply both sides by 4/3

576 [4/3] = r^2

768 = r^2      tale both roots

±√768 = r  = about  ± 27.713

24km  =  24,000m

There are 3600 seconds in one hour

So....

24000 / 3600 = about [6+2/3 ]  m / s

Let  xy = 7    and x + y = -6    

Using the second equation  we have y = -6 - x

So....substituting this into the first equation, we have

x (-6 - x)  = 7 simplify

-6x - x^2  = 7      rearrange

x^2 + 6x + 7 = 0   using the onsite calculator we have

$${{\mathtt{x}}}^{{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{6}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\mathtt{7}} = {\mathtt{0}} \Rightarrow \left\{ \begin{array}{l}{\mathtt{x}} = {\mathtt{\,-\,}}{\sqrt{{\mathtt{2}}}}{\mathtt{\,-\,}}{\mathtt{3}}\\
{\mathtt{x}} = {\sqrt{{\mathtt{2}}}}{\mathtt{\,-\,}}{\mathtt{3}}\\
\end{array} \right\} \Rightarrow \left\{ \begin{array}{l}{\mathtt{x}} = -{\mathtt{4.414\: \!213\: \!562\: \!373\: \!095}}\\
{\mathtt{x}} = -{\mathtt{1.585\: \!786\: \!437\: \!626\: \!905}}\\
\end{array} \right\}$$

So these are the two interchangeable answers for x and y.......

The area of the equilateral triangle with a side of 8 units is given by :

(1/2)* 8^2* [√3]/ 2  = 64√3

The perimeter is 3 * 8   =  24

So the ratio is:

64√3 / 24 =   [8√3] / 3

The sides of this inscribed square will be 2√2. So the perimeter will be four times this = 8√2

I assume this is  -[26 + 3/5]

Note......  3/5 =  .6    so we have

-26.6