Given that, the variable z is directly proportional to x.
So, we can set up an equation as following:
z = kx Where k is constant of variation.
When x= 13, z is 169.
Hence, next sep is to plug in these values in the above equation to get the value of k. Therefore,
169 = k * 13
[tex] \frac{169}{13} =\frac{k*13}{13} [/tex] Divided each sides by 13.
So, k = 13
By plug in k = 13 in the above equation we will get z = 13x.
Now we need to find the value of z when x = 19.
From the above equation we will get:
z = 13 * 19
z = 247
So, z = 247.
I hope this helps you!