Answer:
The number of tablets  200
the number of laptops  40
and, the number of servers 20
Step-by-step explanation:
Let the number of tablets be 'x'
the number of laptops be 'y'
and, the number of servers be 'z'
According to the given question
Total budget = $280,000
Tablets cost = $500 each
 laptops cost = $2000 each
servers cost = $5000 each
Thus, 
500x + 2000y + 5000z = 280,000 ..............(1)
also,
x = 5y  ................(2)
and, 
y = 2z  
or
z =  ............(3)
   ............(3)
substituting y from 2 and 3 in equation 1,  we get
(500 × 5y) + (2000 × y) + (5000 ×  ) = 280,000
) = 280,000 
or
2500y + 2000y + 2500y = 280,000
or
7000y = 280,000
or
y = 40
substituting y in equation 2, we get
x = 5 × 40 = 200
substituting y in equation 3 we get
z =  
or
z = 20
hence, 
 the number of tablets  200
the number of laptops  40
and, the number of servers 20