Final answer:
The theoretical yield is always considered to be 100%, as it represents the maximum amount of product that can be theoretically produced in a reaction. The actual yield is given as a percentage of this theoretical yield.
Step-by-step explanation:
If the actual yield of methyl benzoate obtained is 85% of the theoretical yield, then the theoretical yield by definition is 100%. The question is asking what the theoretical yield is if the actual yield is a certain percentage of it.
Since theoretical yield represents the maximum amount of product that could be produced from a reaction, and the actual yield is a proportion of this maximum, a theoretical yield is always set at 100% for calculation purposes, regardless of the actual yield obtained.