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Set \(x \) as the original number.

Write out equations: 

\(\frac {x-5} {4} = \frac {x-4} {5}\)

Cross-multiply:

\((x-5)5=(x-4)4\)

Simplify to...

\(5x-25=4x-16\)

Solve the equation by subtracting \(4x\) from both sides:

\(x-25=-16\)

Then add \(25\) on both sides:

\(x=-16+25=9\)

So the final answer would be \(x=9\)

we would make the equation (x-5)/4=(x-4)/5 and simplify it into 5x-25=4x-16 when we multiply both sides by 20 and subtract 4x from both sides to get x-25=-16 we then add 16 from both side to get x-9=0 and then we finnaly add 9 to both sides to get x=9