Since y varies directly as the cube of x, y can be calculated by multiplying a constant value "k" by x³, like this:
y = kx³
We are told that y = 17 when x = 4. By replacing 4 for x and 17 for y into the above expression, we get:
17 = k(4)³
From this expression, we can solve for k to get:
17/(4)³ = k
k = 17/(4)³
k = 17/64
Then, we get the following expression of y as a function of x:
y = (17/64)x³
By replacing 3 for x, we get:
y = (17/64)3³ = 459/64 = 7.17
Then, the y is 7.17 when x = 3