y = 3/x to find inverse, switch x and y then solve for y
x = 3/y
y = 3/x is the inverse...... if you put the original function in there , you should get 'x' as a result
y = 3/ (3/x) = x
If you look at the graph of 3/x you might be able to realize it is also the inverse:
https://www.desmos.com/calculator/pycz5hhztx