The x button would help solve the equation/problem
i.e (x+6)squared or 4(2x + 3) +5(x-4)
I know there's a way of doing this on a sheet of paper, but for people to check their answers, i think it would be very useful!

10% of 100.00 is 10, this app shows a total different number, pretty wild.

when a decimal repeats, use this to show that it repeats.

I cannot scroll the conversion type selection. I can select Pressure by clicking the top of the box, which is barely visible, but I cannot select anything below it or read the word Pressure.

Put a button which converts a decimal e.g. 1.5 to DMS 1'30"

Usage: Just type in a value for z (negative or positive) and press the Standard normal distribution table button.

Should also work backwards (then you put in the probability (0<p<1) and get the z instead) using Shift-Button or corresponding.

z values are between ~-3.2 (p=0 for z<-3.2) and 0,000 (p=0.5) and ~3.2 (p=1 for z>3.2)

Add a button where you can type in a system of linear equations and you have to hit the down arrow to tyoe in a new equation to the system or set of equations.

Calculating the Percentage is not correct.... 10-10% should give 1

the history "highlighted" part should be more in contrast with background...chose something like gray

When selecting a number value in the converter view, the selection range is automatically extended to include the unit designator, which makes copy/pasting the value into the calculator view more difficult than it needs to be.

I suggest not auto-extending the selection, allowing the user to only select the numerical portion of the result.

i^2=-1 + 1.224646798818428e-16i the answer suppose to be -1
so why the extra term?

Unit names, like Angstrom, are long and are likely to be accompanied by a long number, especially if not using scientific notation, since the unit size is so small. Converting even a small number like 1 cm to Angstroms results in a large number that is truncated. League is another kind of long name. Not sure what the abbreviation is for that.