Well it’s pretty easy 7 - 15 is 8
        
             
        
        
        
Aqueduct carries water over a long distance.
        
             
        
        
        
No! matter is not created nor distroyed
        
                    
             
        
        
        
No the amplitude of each waves are different on different cardiac cycles. 
<u>Explanation:</u>
- The PQRST waves are used to represent the atrial and ventricular depolarization and repolarization.  These waves are reflected in ECG.  
- In this as the series, p occupies the first place then QRS complex and at last T wave. In the QRS wave complex,  R wave is said to be the largest wave.  
- The direction and amplitude of r wave depend on the electrical picture. The R wave represents the ventricles depolarization so it is the largest wave.
 
        
             
        
        
        
On this World Meteorological Day, celebrated each year on March 23, we climb far above the Earth for a view of the southern Peruvian coast courtesy of the Landsat 8 satellite. Below the clouds, at the bottom of those canyons, are the Yauca and <span>Acarí </span>Rivers, which drain into the Pacific. As any good meteorologist taking a break from today’s celebrations will tell you, warm air from the equator forms a layer over the cool coastal air here, pushing the clouds into the deep river canyons and covering the Pacific Ocean shore.