C# Missing operand ofter '-' operator [on hold]

I can believe that I can get right this. It's a simple if statement. It's my first time trying it in c#

if (Age == "More12") Age = "You are a grown up";

It gives me this error

"Syntaxis Error: Missing operand ofter '-' operator"

I tried a lot of combinations and checked a lot of similar question. Nothing is working

Someone please?