Explanation:

Given
Total number of students in class A and B = 92
Number of students in class A = Number of students in class B + 30% of the number of students in class B
Average weight of students of class A and B = 56
Average weight of students of class B = Average weight of students of class A+ 50% of average weight of students class A
Concept
Combined meanXAB = [(number of students in class A x Average weight of student of class A) + (number of students in class B x Average weight of student of class B)/(Total number of students in class A and B)
Calculation
A+B=92
A =B + 30% of B
A 1308/100
=A=130 (92-A)/100
=A=(11960-130A)/100
100A = 11960-130A
=230A = 11960
=A=52
B=92-52
=40
Let the average weight of students of section A = x
Average weight of students of sectionB = x + 50% of x =150x/100
56 = 52xx+40 x 1.5x)/92
56 x 92 52x+60x
=5152 = 112x
⇒x=5152/112
⇒x=46
B = x + 50% of 46
=46 +23
=69
The average weight (in kg) of students in B le 69.