What is the chemical formula of a trisaccharide made of three bonded glucose molecules?

(6 C, 12 H, 6 O) x 3 - (H20) x 2 = 18 carbons, 32 hydrogens, 16 oxygens

the answer is C18H32O16

because you use 2 water molecules to form molecule ... so you are losing 4 H molecules and 2 O molecules). the first 2 glucose molecule combine losing one water molecule; and the third combines to them, losing another water molecule.