The question is asking how much soy sauce Bonnie is mixing per every millilter of vinegar. To calculate this ratio, we simply divide the amount of soy sauce she mixed by the total amount of vinegar she used. This leads to
[tex]\frac{150\text{ (soy sauce)}}{100\text{ (vinegar)}}[/tex]which is equals to
[tex]\frac{150}{100}=\frac{30\cdot5}{20\cdot5}=\frac{30}{20}=\frac{3}{2}=1.5[/tex]so Bonnie uses 1.5 ml of soy sauce per every ml of vinegar
