A. 15
Explanation
Step 1
the proportion between eggs hidden and eggs not found is:
[tex]\text{proportion}=\frac{eggs\text{ hidden}}{\text{eggs found}}=\frac{8}{3}[/tex]
Step 2
if
this year the Roberts family hid 40 eggs,then
Let x represents the number of not found eggs
the proportion is the same
[tex]\begin{gathered} \\ \frac{8}{3}=\frac{40}{x} \\ \text{solve for x} \\ 8x=40\cdot3 \\ x=\frac{40\cdot3}{8} \\ x=\frac{120}{8} \\ x=15 \end{gathered}[/tex]So, the answer is A.15