2m+8n-mn=0 means 2m+8n=mn, and both sides of the equation are divided by mn.

2/n+8/m= 1

m+n =(m+n)* 1 =(m+n)*(2/n+8/m)= 2m/n+8n/m+2+8

2m/n+8n/m & gt； =2√(2m/n*8n/m)=8

Take the equal sign when 2m/n = 8n/m.

M=2n, you can get the equal sign, m+n = 2m/n+8n/m+10 > =8+ 10= 18

So the minimum value of m+n is 18.