For the first table, e is elephant and b is beavers. We are basing the number of beavers on the number of elephants, therefore, elephants is just e, while beavers is e = 3b. For the second table, children's tickets are c while adults are a. We are basing the cost of the child ticket on the adult ticket, so the adult ticket is just a, while the child's ticket is a - 6.