Suppose that $60\%$ of the eighth graders and $30\%$ of the seventh graders at Washington Junior High participate in MATHCOUNTS. There are $150\%$ as many eighth-graders as there are seventh graders at the school. What percentage of the seventh and eighth graders, taken together, participates in MATHCOUNTS?

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)