What is the answer? I find this very confusing for me.

Answer:
19
Step-by-step explanation:
If you want to find the answer of the equation, sub the given information into it:
z + xz + y
we know that:
x = 5
y = 1
z = 3
We got:
= 3 + 5*3 + 1
= 3 + 15 + 1
= 19
Hope this helped :3