The total number of pencils that is available all together = 684 pencils.
Number of boxes of pencils found = 12
Each box contains = 12 pencils
The total number of students = 54
Each student brought = 10 pencils
The total number of pencils all together = Total number of pencils from all students + total number of pencils in all boxes
Total number of pencils in all boxes:
[tex]\begin{gathered} =\text{ 12}\times\text{ 12} \\ =\text{ 144 pencils} \end{gathered}[/tex]Total number of pencils from all students:
[tex]\begin{gathered} =\text{ 54 }\times10 \\ =\text{ 540 pencils} \end{gathered}[/tex]The total number of pencils all together = 144 + 540
The total number of pencils that is available all together = 684 pencils