Create an algebraic equation.
Everything is = 900g
Create what you trying to find as: x.
Sugar = x
You have twice as much butter as sugar,so:
Butter = 2x
You have 1.5x as much flour as butter,so:
Flour = 3x
900g = x + 2x + 3x
900g = 6x
You want to find sugar (x). So divide by 6
150g = x
She needs 150g of sugar.
900g