So what you do first is simplify the top equation
m-6(n+2)=-8
m-6n-12=-8
Add 12 to both sides to get
m-6n= 4
Next solve for m.
Add 6n to both sides
m=6n+4
Plug that into the second equation for m.
6n+(6n+4)=16
Combine like terms. 6n+6n is 12n so...
12n+4=16
Solve for n by subtracting 4 to each side
12n=16-4
12n=12
n=1
Plug n=1 into the m equation or any of the two original equations to solve for m...
6(1)+m=16
6+m=16
m=10
Since you solved for m earlier you could also do it this way:
m=6(1)+4
m=6+4
m=10
Thus your two solutions are m=10 and n=1
Hope this helps!!!!!