Answer:
(C) 9/5
Step-by-step explanation:
There are several ways to go at this. Here's one of them.
Multiply the second equation by 9/9, then substitute for 9y from the first equation.
(9y)/(9z) = 7/5
(7x)/(9z) = 7/5
Now, multiply by 9/7.
x/z = (9/7)(7/5) = (9·7)/(5·7)
x/z = 9/5
