hey i really need help with a formula because i don't know which one to use.
i have this information

0-10000 = O% tax
10000-90000 = 20% tax
90001-100000= 30% tax

and i have a lot of values for it but i dont know how to make it like simple
to work out as one formula like the IF statement can be used if it only had
to variables but it has three and i dont know what formula to use.
please help its really important

thank you heaps.