3=(21.25-t)/t

3=(21.25-t)/t

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Let's start by multiplying both sides by "t"......note, we are explicitly assuming that "t" isn't = 0

(and it's not!!!)  ...   so we have

3t = 21.25 - t       .....now add t to both sides......we have

4t = 21.25            .....divide both sides by 4

t = 21.25 / 4   =    5.3125