Answer
$\frac{13}{25}$
Work Step by Step
Using the Venn Diagram, we see that $104$ students liked mustard only (not mayo or both). So, the fraction of the students that liked mustard only is $104$ out of the total $200$ students surveyed.
Since we're asked for an answer "in lowest terms" we must simplify this fraction of $\frac{104}{200}$ to get the final answer.
To do this, we find the largest number that divides by both $104$ and $200$ which is $8$. Dividing both top and bottom each by $8$ we get
$$\frac{104}{200}=\frac{13}{25}.$$
