C++

Which of the following variable declarations are correct? If a variable declaration is not correct, give the reason(s) and provide the correct variable declaration.

double conversion = 2.5; //Line 1

char grade = 'B+'; //Line 2

double 28.5 = num. //Line 3

string message = ' 'First C++ course'; //Line 4

int age = 18 years //Line 5

int perfectSquare; //Line 6

float x, y, decimal; //Line 7