在令牌“=”中键入语法错误，在此令牌之后期望表达式(矩阵乘法)

I'm trying to create a method produto to multiply matrices that will not be received by user input so I put a some matrices examples to test the code inside main. Right now I'm getting error "Syntax error on token "=", Expression expected after this token - line 15" Any help? to multip