5/4+x=3/4 how do I figure this out

You could subtract 5/4 from each side of the equation.
Then it would say
                                 x = -2/4 .

That's a perfectly true solution, but not a very attractive one.
To pretty it up, you could simplify the fraction if you felt like it,
and you would have
                                   x = -1/2 .

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