Answer: 3.2 tons
Step-by-step explanation:
We know that 1 ton = 2000 pound
Then , 
Given : Mustafa’s horse ate 6,400 pounds of hay last year.
Then, the number of tons of hay his horse ate last year is given by :-

Therefore, the number of tons of hay his horse ate last year = 3.2 tons
6.5 is the mean of the data
1/2x + 42 = 4x
-1/2x -1/2x
------------------------
42 = 3.5x
/3.5 /3.5
------------------------
12 = x
the number is 12
explanation: 42 more than 1/2 of a number can be written as 1/2x + 42
four times a number can be written as 4x.
42 more than 1/2 of a number is equal to 4 times a number. So 1/2x + 42 = 4x.
Hope this helps :)