You should state your problem more clearly with correct Order of Operation symbols because the "3/x-4" part can be either recognized as "3 / (x-4)" or "(3/x) - 4"

But anyway for "3 / (x-4)" I cross multiplied and got 3x = 5(x - 4) and use the distributive property on the right side to get 3x = 5x - 20

Then I subtract 5x from both sides and end up with -2x = -20

Divide both sides by -2 and get x = 10

For "(3/x) - 4" I first found a common denominator for the lone '4' by multiplying its denominator (invisible '1') by x and multiplying the numerator as well to get '4/x' so the equation looks like: (3/x) - (4x/x) = 5/x

Then I combined the left side to get (3 - 4x) / x = 5/x

Then I cross-multiply again to get: x(3 - 4x) = 5x

Use distributive property on the left side to get: 3x - 12x^2 = 5x

Looks like a quadratic equation so I move everything over to one side: 12x^2 + 5x - 3x = 0

Then use the quadratic formula to get the solutions: x = 1/3 or x = -3/4

Be sure to check those answers