How to do this math problem: There are 507 garlands in Grade Four, Five and Six. If there are 80 garlands in level 6, it is three times that of level 5, and level 4.
One word is missing. Are there 20 words missing in the fourth grade?
Number of fifth graders = (507+80+20)/(3+1+0.5) =126 (pieces)
Four-level quantity = 126*0.5+20=83 (pieces)
Six-level quantity = 126*3-80=298 (pieces)