If Ty can make 7 signs in 2 hours that means in 4 hours he could double that output to make 14 signs. Harrison, on the other hand, makes 15 signs every 4 hours. Therefore, by default - Harrison makes 1 more sign every 4 hours than Ty. Harrison has the greater rate. You have to figure out how many signs Ty can make in 4 hours, by multiplying 2 x 7 = 14. Hope that helps.
