This is what i got so far... not sure why it's not compiling.... or if it's right :/

Code:

#include <iostream>
#include <string>
int main()
{
std::string grade;
std::string minus;
std::string plus;
minus = "-";
plus = "+";
std::cout << "Enter your grade %: ";
std::cin >> grade;
if (grade <= 60) {
std::cout << "You scored an F\n"; }
if (grade > 61 && grade <= 70) {
std::cout << "You scored a D\n"; }
if (grade.substr(1, 1) <= 3) {
std::strcat (grade, minus) }
if (grade.substr(1, 1) = 8 || 9 || 0 {
std::strcat (grade, plus) }
if (grade > 71 && grade <= 80) {
std::cout << "You scored a C\n"; }
if (grade.substr(1, 1) <= 3) {
std::strcat (grade, minus) }
if (grade.substr(1, 1) = 8 || 9 || 0 {
std::strcat (grade, plus) }
if (grade > 81 && grade <= 90) {
std::cout << "You scored a B\n"; }
if (grade.substr(1, 1) <= 3) {
std::strcat (grade, minus) }
if (grade.substr(1, 1) = 8 || 9 || 0 {
std::strcat (grade, plus) }
if (grade > 91 && grade <= 100) {
std::cout << "You scored an A!\n"; }
if (grade.substr(1, 1) <= 3 {
std::strcat (grade, minus) }
if (grade.substr(1, 1) = 8 || 9 || 0 {
std::cat (grade, plus) }
}