Short solution:
b is the number of students
The coefficient, 300, depends on the number of students, b, because they are multiplied.
so this tells you your answer has to be the parts of the breakdown that mention students
only Training gear, food and miscellaneous depend on the number of students.
This automatically leaves B and D as your potential answers.
The question tells you it's Mr browns TOTAL cost for a 3 day trip, so you know it's B
Detailed solution
for a 3 day camping trip:
Camping rental @ $200/day = $200 x 3 = $ 600
Training cost per student per day @ $20/student/day = $20 x 3 x b students= $ 60b
Food @ $30/student/day = $30 x 3 x b students= $ 90b
Miscellaneous expenses@ $50/student/day = $50 x 3 x b students= $ 150b
Camp gear is a one-time payment of $1050
Mr Brown's total expense = $ 600 + $ 60b + $ 90b + $ 150b +$1050
Sum like terms: $ 600 +$1050 + $ 60b + $ 90b + $ 150b = $1650 + $300b
so 300 is the sum of the total cost over 3 days per student for training gear, food, and miscellaneous.
