ANSWER
The other zero is

EXPLANATION
The axis of symmetry serves as the midpoint of the two zeroes.
We were given that the axis of symmetry of the quadratic equation is

We were also given that, one of the zeroes of the quadratic equation is

Let the other zero of the quadratic equation be

,then, we apply the midpoint formula to find the value of

Since it is the x-values of the intercepts that gives the solution, we use only the x-value part of the midpoint formula which is given by,

We substitute to obtain,

We multiply through by 2 to get,

This implies that,

Since both of the numbers have a variable which is x ready to be multiplied, there is no expression leading to the variable therefore you will add normally but you will need to put the missing variable which needs to be multiplied. So overall you can just add and once you get your variable you can be abe to multiply and get your final answer.
Hope this helps
Recall the logarithm rules :
a^y = x is the same as log_a x = y
In this case,
a = 18
y = r - 10
x = 93
So,
18^ (r-10) = 93
is the same as
log_18 93 = r - 10
Solve for r to get :
10 + log_18 93 = r
One
the gcf all the numbers is 1