is this correct :

solve for n

0.6 (n+10)=3.6
0.6n+6=3.6
0.6n=3.6-6
0.6n=-2.4
n= -2.4/0.6
n=-4

yes, but...

I would have divided both sides of your equation by 0.6 to get
n+10 = 6
n = 6-10
n = -4