Answer:
C
Explanation:
We know that the cost of a glue stick is proportional to the quantity
Thus, you could create a proportion for 4 glue sticks costing $7.76 (4 / 7.76) and 13 glue sticks costing $x (13 / x), where you'd need to solve for x by cross multiplying:

When we do the math, we see that 4 / 7.76 simplifies to about 0.51 and 13 / 25.55 also simplifies to about 0.51, showing the the two fractions are proportional.