A multiple of 7 between 80 and 90

One of the multiples would be 84. It is pretty easy you just have to times 7 by numbers higher than 12 until you'll get to the maximum number before 90.

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)

25 inches - 0.694 yards