18 + 13 = 31
It is: 5+13+18 = 36
(13+5)18=13+(5+18)
5 + -13 + 18 = 5 - 13 + 18 = 10
20+18+13+9=60
13 plus -8 = 5 ... and -18 plus -2 = -20.
18 + 13= 31
18 + 13% = 18 x (1 + (13/100)) = 18 x 1.13 = 20.34
17 + 14 + 17 + 19 + 18 + 13 + 11 = 109
No.
13 + 5 = 18
80
-13