Answer:
z=312 if you meant x=26
Step-by-step explanation:
Direct proportional means there is a constant k such that z=kr. k is called the constant of proportionality. The constant k will never change no matter your (x,z).
So using our equation z=kr with point (18,216) we will find k.
216=k(18)
Divide both sides by 18
216/18=k
k=216/18
Simplify
k=12
So we now know the equation fully that satisfies the given conditions of directly proportion and goes through (x,z)=(18,216).
It is z=12x.
Now we want to know the value of z if x=26.
Plug it in. z=12(26)=312
z=312
