Alan

5000J of energy would melt 33.5 gm of gold, so the final temperature would be it's melting point, 1064°C (and it would be liquid!) 

$${factor}{\left({\mathtt{44}}\right)} = {{\mathtt{2}}}^{{\mathtt{2}}}{\mathtt{\,\times\,}}{\mathtt{11}}$$

This means 44 can be divided exactly by 2, 4, 11, 22 (=2*11) (as well as 1 and 44 of course).

VAT = (531-450)/450*100 %

$${\mathtt{VAT}} = {\frac{\left({\mathtt{531}}{\mathtt{\,-\,}}{\mathtt{450}}\right)}{{\mathtt{450}}}}{\mathtt{\,\times\,}}{\mathtt{100}} \Rightarrow {\mathtt{VAT}} = {\mathtt{18}}$$

VAT = 18%

If he's got 100 feet of fence the length is 100 feet whatever the shape!  I suspect you mean what shape maximizes the enclosed area, in which case the answer is a circle.

3x + 2y = 7  ...(1)

3x + y  = 11 ...(2)

Subtract (2) from (1)

y = -4

Put this in (2)

3x - 4 = 11

3x = 15

x = 5

0.05" = (0.05/3600)°

$$\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{tan}}{\left({\frac{{\mathtt{0.05}}}{{\mathtt{3\,600}}}}\right)} = {\mathtt{0.000\: \!000\: \!242\: \!407}}$$

Volume of a cylinder is pi*(diameter/2)²*height.  You can plug the numbers in using the calculator on the home page here. 

The exterior angle must be 180°-150° = 30°, and we have n*30° = 360° so n = 12.  It's a regular dodecagon.

There's a well known right-angled triangle with sides of 5, 12 and 13.  If sin(B) = 12/13 then tan(B) must be 12/5.