Answer:
The mass in grams of each element in the body of 62 Kg are
Oxygen               40300 g
Carbon                11160 g
Hydrogen            6200 g
Nitrogen              1860 g
Calcium                992 g
Phosphorus         744 g
Other elements   744 g
It is possible to check it adding all the components, the total is 62000 g.  
Explanation:
Firstly, we have a total mass of 62 Kg and the composition as a percentage of each component. 
                             Percentage ( %)
Oxygen               65.0
Carbon               18.0
Hydrogen            10.0
Nitrogen              3.0
Calcium               1.6
Phosphorus         1.2
Other elements   1.2
Taking the definition of a percentage as part of hundred total, each percentage can be expressed as a decimal number. We should divide the percentage with 100 of total. For example: Oxygen 65%, it means 65/100 = 0.65. So, Oxygen is 0.65 in decimal numbers. We do the same for each component.
                            Percentage ( %)      Decimal number
Oxygen               65.0                         65/100 = 0.65
Carbon               18.0                           18/100 = 0.18
Hydrogen            10.0                         10/100 = 0.10
Nitrogen              3.0                           3/100 = 0.03
Calcium               1.6                           1.6/100 = 0.016
Phosphorus         1.2                           1.2/100 = 0.012
Other elements   1.2                           1.2/100 = 0.012
Finally. We can multiply decimal number of each component taking the total. 1 Kg is equivalent to 1000 g. 
So, 62 Kg = 62 * 1000 g = 62000 g
After that we get the mass in grams of each element, by multiplying 62000 g and the decimal number of each component as follows: 
                            Percentage ( %)      Decimal number      Mass in grams (g)         
Oxygen               65.0                         65/100 = 0.65         0.65*62000=40300
Carbon               18.0                           18/100 = 0.18         0.18*62000=  11160
Hydrogen            10.0                         10/100 = 0.10         0.10*62000=   6200
Nitrogen              3.0                           3/100 = 0.03          0.03*62000= 1860
Calcium               1.6                           1.6/100 = 0.016        0.016*62000= 992
Phosphorus         1.2                           1.2/100 = 0.012        0.012*62000=744
Other elements   1.2                           1.2/100 = 0.012        0.012*62000=744