Answers in log or ln form?

Looks like <Shift><Mode> <down arrow> <1>

Give it a shot. I have attached the manual.

Good luck.

Paul
http://support.casio.com/pdf/004/fx-115ES_991ES_Eng.pdf

Your answer is 6.7*10^18. That requires 19 places on the display: There are not enough places to write that. Besides, calculators are deigned to use Scientific Notation whenever the result to be displayed is too large or too small.
If you enjoy writing zeros, convert by hand the scientific notation into what you call long number.

Press [SHIFT][ division key]. It is marked with nCr.

You should try to explore the calculator to find its capabilities. You can also read the manual. Everything is in it.
Press the Mode button, then the down arrow key. On the second page of the mode list you find 2:Verif

Select the Math input/output mode by pressing SHIFT [SETUP] 1.

[SETUP] is the shifted function of the MODE key, located just right of the round cursor pad.

If it does not have the FACT key, you must factor by hand: Divide by 2, then by 3, 5, 7 etc.

To convert a single answer from symbolic to decimal, press the S--D key (just above the DEL key). To have all answers come out in decimal format, press SHIFT MODE 2 to switch to the LineIO mode.

By 'log inverse', you presumably mean the inverse of the logarithm function. There are two logarithm functions on most scientific calculators. Firstly [ln], or natural logarithms, to the base e, where the inverse is e^x. Secondly [log], or logarithms to the base 10, where the inverse is 10^x.

Example 1 : ln(2) = 0.69314718 so e^0.69314718 = 2
Example 2: log(2) = 0.301029995 so 10^0.30102995 = 2

You can calculate the logarithm to any base by using the relationship
logb(x) = log(x)/log(b) = ln(x)/ln(b).

To calculate the log base 2 of 16, either divide the log of 16 by the log of 2 or the ln of 16 by the ln of 2.

You seem to be doing it correctly. The natural logarithm of 2/3 is about -0.405 and the natural log of 1/30 is about -3.401.

As for the common log of 10y, that would depend on the value of y. If y is e/10, then the log of 10y would be about 0.4343.