Alan

You are quite right Anonymous!  I've now corrected my original.

Another possibility:

 $$\frac{6}{3}+4*5=22$$

You haven't provided enough information for a unique answer!

There is an interesting novel about the Goldbach conjecture, called Uncle Petros and Goldbach's Conjecture by  Apostolos Doxiadis.  The publishers (Faber) offered a $1 000 000 prize to anyone who proved the theorem within 2 years of its initial publication (in 2000).  Needless to say, no-one claimed the prize!

I'm afraid this question reads like gobbledygook to me blaster0!! Have you typed it in correctly?

If this is log to the base 10, then log y = 3.8 means that y = 10^3.8

$${\mathtt{y}} = {{\mathtt{10}}}^{{\mathtt{3.8}}} \Rightarrow {\mathtt{y}} = {\mathtt{6\,309.573\: \!444\: \!801\: \!932\: \!494\: \!3}}$$

If it is log to a different base, say, b, then y = b^3.8.

The final value here is given by

$${\mathtt{finalvalue}} = {\mathtt{6\,000}}{\mathtt{\,\times\,}}{\left({\mathtt{1}}{\mathtt{\,\small\textbf+\,}}{\mathtt{0.09}}\right)}^{{\mathtt{4}}} \Rightarrow {\mathtt{finalvalue}} = {\mathtt{8\,469.489\: \!66}}$$

So final value = $8469.49

So the interest earned is 

$${\mathtt{8\,469.49}}{\mathtt{\,-\,}}{\mathtt{6\,000}} = {\mathtt{2\,469.49}}$$ dollars

Assuming the scores obey a normal distribution the following cumulative probability graph should help:

This is the cumulative probability for a normal distribution with mean 0 and standard deviation of 1.

Here we have z = (Joelie's test score - mean test score)/standard deviation

We can see from the graph that to get into the top 20% (ie reach a cumulative probability of 0.8) z must be at least 0.842.  So:

0.842 = (0.75 - 0.62)/stddev

$${\mathtt{stdev}} = {\frac{\left({\mathtt{0.75}}{\mathtt{\,-\,}}{\mathtt{0.62}}\right)}{{\mathtt{0.842}}}} \Rightarrow {\mathtt{stdev}} = {\mathtt{0.154\: \!394\: \!299\: \!287\: \!410\: \!9}}$$

So the standard deviation is 0.154 or 15.4%.

At least, I think this is what you are after!

Depending on the browser you are using you should be able to zoom in on the calculator.  In Google Chrome, at the top right of the window are three, vertically spaced, horizontal bars. Click on this and you should see a zoom option.  In Internet Explorer near the top right of the window is a cog-wheel icon.  Again, click on this and you should find a zoom option.

Assuming z is not zero, then z/z = 1, so:

$${\mathtt{Y}} = {\mathtt{\,-\,}}{\mathtt{30}}{\mathtt{\,\times\,}}{\mathtt{3.009\: \!265\: \!9}}{\mathtt{\,-\,}}{\mathtt{3.068\: \!983\: \!5}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,-\,}}{\mathtt{1}} \Rightarrow {\mathtt{Y}} = -{\mathtt{97.415\: \!944}}$$