Desmos, conveniently, will calculate percentages directly. You can enter an expression using the percent sign (%) and Desmos will politely add "of" so you know exactly what's happening, and it will perform the percentage calculation so you don't need to convert values between decimals and percentages. For example, entering "45%" will produce "45% of", which you can then complete with, say, "45% of 20", and Desmos will perform the calculation for you. Of course, you should be able to set up an expression to find 45% of 20 without Desmos's help, but because Desmos can also solve equations using regression, and it can plot solutions using graphing, you can form statements like "p% of 20 ~ 9" and Desmos will solve for p directly, returning p = 45. Alternatively, if you preferred a graphing approach, you could enter "x% of 20 = 9", and Desmos will plot a solution line at x = 45. These techniques are very handy while also contributing to the worrisome spread of innumeracy among the populace.