You subtract and find x=10
There is no quotient: if x is equal to zero, then your problem would simplify to a number divided by zero. As it is impossible to divide by zero, there is no answer.
If there are no options to choose from I’d say 25 but if there are options please post them
Price elasticity is defined as

.
Here, the question has omitted to define variables, so we will ASSUME
p=price
x=variable,
and we're given
p+x^2-160=0
We calculate

by implicit differentiation with respect to p:
1+2x (dx/dp)=0
=>
E(x)=(dx/dp)=-1/(2x)
Therefore the price elasticity at x=65 is
E(65)=1/(2*65) =-1/130 (approximately -0.00769)
So,
We need to convert qt. to c.
4 c. = 1 qt.
8 * 4 = 32 cups
Thomas will make 32 1-cup servings of soup.