18) 12-(x+4 7/15)=5 13/15

12 - (x + 4 + 7/15) = 5 + 13/15

12 - x - 4 - 7/15 = 5 + 13/15

8 - 7/15 - x = 5 + 13/15

x = 8 - 5 - 7/15 - 13/15

x = 3 - 20/15

x = 3 - 4/3

x = 9/3 - 4/3

x = 5/3