How do you figure out this equation: 6/51=3/x?

Basically a simple proportion/rate/ratio

6 : 51 = 3 : ?
If you don't understand this is that as an analogy in english:
6 is to 3 as 51 is to ?

Well? 3 is half of 6 so whatever ? is, it's half of 51!

51/2 =
25.5

Hope that helps and correct me if I'm wrong!

Cross multiply the equation as shown:
6          3
_    =    _

51         x

6(x)=3 x 51
6x=153
x=25.5

Check your solution:
6/51=3/25.5
3/25.5=3/25.5           (Divide 6 and 51 by 2)

Hope this helps :)

Use a graph site then you will find your answer