Data Sufficiency

A contractor combined x tons of a gravel mixture that contained 10 percent gravel G, by weight, with y tons of a mixture that contained 2 percent gravel G, by weight, to produce z tons of a mixture that was 5 percent gravel G, by weight. What is the value of x ?

(1) y = 10

(2) z = 16

I marked C while doing this question in GMAT Prep, but OA is D.
Can anybody explain this question?

alligation approach
x-------z-----y
10 -5-- 5 -3--2
10 -3---5 -5--2
1.y = 10 , x & y are in ration of 3:5 hence x = 6. sufficent
2.ammount of x = 3/8*16(z resulting ammount of combined mixture)= 6, sufficent

vipulgoyal wrote:alligation approach
x-------z-----y
10 -5-- 5 -3--2
10 -3---5 -5--2
1.y = 10 , x & y are in ration of 3:5 hence x = 6. sufficent
2.ammount of x = 3/8*16(z resulting ammount of combined mixture)= 6, sufficent

I am unable to understand what you wrote.
What is alligation approach?
Could you please explain alligation approach in detail.

please refer below link, still have any query please let me know
https://www.beatthegmat.com/ratios-fract ... 15365.html

vipulgoyal wrote:please refer below link, still have any query please let me know
https://www.beatthegmat.com/ratios-fract ... 15365.html

Thanks man!