We know there is 57 members are in the math club and there is twice as many sixth grades than the seventh. To find out how many sixth graders are in the club, we do:
x = seventh graders
2x = sixth graders
2x + x = 3x
57=3x
57 ÷ 3 = 3x ÷3
19 = x
So there is 19 seventh graders and 19×2= 38 sixth graders
