Algebra 2 homework

Question

I don’t understand how to put it together

The county fair is a popular destination. This year the senior class at high school A and the senior class from high school B both planned trips there. The senior class from high school A rented and filled 12 vans and 11 buses with 719 students. High school B rented and filled 6 vans and 12 buses with 678 students. Each van and each bus carried the same number of students. Find the number of students in each van and in each bus.

Answer 1

12v + 11b = 719

-2(6v + 12b) = -2(678)

12v + 11b = 719

-12v - 24b = -1356

-13b = -637

b = 49

12v + 11(49) = 719

12v + 539 = 719

12v = 180

v = 15