Answer: A) 350mL of shampoo and 495 mL of conditioner.
Step-by-step explanation: this problem is solved by a system of two equations, the first one will be the sum of the volumes of the two bottles that equals 845 milliliters:
x+y=845
and the second one will be the sum of the used fractions of shampoo and conditioner, that equals 64 milliliters:
![(2)/(35)x+(4)/(45) y=64](https://img.qammunity.org/2020/formulas/mathematics/middle-school/umn5mk4d0uz69o41ples9re3ma4qeh7awe.png)
so, for the first equation we have that:
x=845-y
and we substitute this expression into the second equation:
![(2)/(35) (845-y)+(4)/(45) y=64](https://img.qammunity.org/2020/formulas/mathematics/middle-school/nu2i3x7krlcqsmf5ubjhzkksz00ftywzhg.png)
and we solve:
![(1690)/(35)-(2)/(35)y +(4)/(45) y=64\\\\](https://img.qammunity.org/2020/formulas/mathematics/middle-school/3f4q233guxvvh6iu6orih9yh5kpxwdrpy2.png)
![(1690)/(35)+((-18y+28y)/(315))=64](https://img.qammunity.org/2020/formulas/mathematics/middle-school/af7ls0khpraohzkcapuk0jv6e97zols87h.png)
![(1690)/(35) +(10y)/(315)=64](https://img.qammunity.org/2020/formulas/mathematics/middle-school/kb26x8oqhxkk7mkxtl07u1f0bg49ttpf58.png)
![(2y)/(63)=64-(1690)/(35)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/y4sgxp2j8kgqxvcyiyzj9x6vi3av6pc3zn.png)
![(2y)/(63)=(110)/(7)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/k6l38gh8xx7864o3pq3lrj3leg0pnii79v.png)
y=495
now with the first equation:
x=845-y
x=845-495
x=350
The shampoo is 350ml and the conditioner is 495ml.