<p>Section 7:
16. If y = (5x^3)/z, what happens to the value of y when both x and z are doubled?
You can do this by plugging in numbers. Although most books say avoid plugging in 1, in this case plugging in 1 for both x and z should work, since the result should be true for any nonzero x and z.</p>
<p>Plug in x =1 and z = 1. Then y original = 5.
Now double both x and z. So plug in 2 for both x and z. Then y final = 20. So y is multiplied by 4.
Answer: E</p>