(2.3 + 1.5 +13.18+ 4.5 + 5.18 +1.3):2
2,3+1,5=3,8 3,8+13,18=16,98 16,98+4,5=21,48 21,48+5,18=26,66 26,66+1,3=27,96 27,96:2=13,98