If and , what is the value of ​ expressed as a common fraction?

2x  =  5y     ⇒    y  =  (2/5)x      (1)

7y = 10z     (2)

Sub  (1)  into (2)

7 [(2/5)x]  = 10z

[14/5] x  =  10z

z / x  =   14 / 50   =   7 / 25

Well, young person! Here is another FAST answer!

x=12.5, y=5, z=3.5, So:

z/x = 3.5 / 12.5 =1 / (3 4/7) =7/25

thanks, guest!