When Carla looked out at the school parking lot, she noticed that for every 2 vans, there were 5 trucks. If there were 84 total vehicles in the parking lot, how many of them were trucks?

38+105= 143, 39+104=143, and you will find then adding the numbers on opposite sides, moving inwards yields the answer 138 every time. because of this, you’re going to multiply 138 times the number of pairs, which is 34. therefore, 34*138= 4692(i’m sorry if it’s the wrong numbers, but it’s the right concept)