It is called subscript indicating the number of atoms.
Explanation:
The chemical compound is formed by two or more elements.
The compound is formed by the sharing, accepting or donating the electrons. 
The compound formed by two elements will have different valencies of cations and anions.
In chemical formula of compound specific number of atoms of each element are present. 
eg: H2O (2 atoms of hydrogen bonded with one atom of oxygen)
        NaCl  (1 atom of sodium and one atom of chloriine are bonded.)
      NaHCO3 ( 1 atom of sodium, 1 atom of hydrogen, 1 atom of carbon and 3 atoms of oxygen.) 
 
        
             
        
        
        
Answer: If you are 80 years and older, it should be less than 150/90 (“150 over 90”). In general, the lower your blood pressure, the better. A blood pressure reading of less than 90/60 is normal as long as you feel okay.
 
        
             
        
        
        
Answer:
To maintain body homeostasis
Explanation:
The endocrine system consists of the endocrine glands that release hormones directly int the blood. Those hormones bind to their receptors on the target cells and thus regulate their function. The major glands are: 
pineal gland-releases melatonin, controls sleep cycle
pituitary gland-control growth, blood pressure, thyroid glands and metabolism etc.
pancreas-secretes insulin and glucagon, control of blood sugar levels 
ovaries, testes-reproductive role (release female and male hormones)
thyroid gland-controls metabolism and protein synthesis
parathyroid gland-controls Ca levels
hypothalamus-connects nervous and endocrine systems, controls other glands 
adrenal glands-release adrenalin and steroid hormones.
 
        
             
        
        
        
Answer:
18ft
Explanation:
because there are 18 blocks total 9 blocks at the bottom 6 in the middle and 3 at the top.