SOUTH CAROLINA -- A South Carolina English teacher has gone viral for correcting a letter from the president.Yvonne Mason has been teaching for 17 years, and says she's caught plenty of "silly mistakes."She said she was very surprised to see so many silly mistakes in a letter received from President Donald Trump.So Mason decided to correct the letter and send it back to the White House.The letter was in response to a letter she wrote the president after the deadly shooting at Parkland High School.