According to the information given, building and solving an expression, it is found that she used 1400 g of flour for the cakes.
Hence, the expression is:
[tex]\frac{x}{5} + \frac{4x}{15} + 750 + 850 = x[/tex]
[tex]x - \frac{x}{5} - \frac{4x}{15} = 1600[/tex]
[tex]\frac{15x - 3x - 4x}{15} = 1600[/tex]
[tex]8x = 15(1600)[/tex]
[tex]x = 15(200)[/tex]
[tex]x = 3000[/tex]
For the cakes:
[tex]C = \frac{x}{5} + \frac{4x}{15} = \frac{3000}{5} + \frac{4(3000)}{15} = 600 + 800 = 1400[/tex]
She used 1400 g of flour for the cakes.
A similar problem, also involving an expression, is given at https://brainly.com/question/26142208