Students in grade 3 and grade 4 in a primary school donate nuts for poor students. The number of nuts from 3 classes of grade 4 is 12kg more than the number of nuts from 3 classes of grade 3 and 3kg less than the number of nuts from 4 classes of grade 3. What is the number of nuts donation from 1 class of grade 3, 1 class of grade 4, given that each  grade has the same number of nuts donation.