math

1/2m-4=5

       +4+4

1/2m=9

x2.   x2

m=18

there are two possible ways your problem can be interpreted:

 

1) if you meant (1/2m)-4=5

then:

1/2m=9

1=18m

m=1/18

 

2) if you meant 1/(2m-4)=5

then:

1=5(2m-4)

1=10m-20

21=10m

m=21/10