Answer:
15.
[tex]\left\{\begin{array}{l}x+y=50\\0.2x+0.1y=6\end{array}\right.[/tex]
16. 10 ml of 20% saline and 40 ml of 10% saline
Step-by-step explanation:
A chemist takes x ml of 20% saline and y ml of 10% saline. In total, he takes
x + y ml that is 50 ml, so
[tex]x + y = 50.[/tex]
There are [tex]0.2x[/tex] ml of salt in x ml of 20% saline and [tex]0.1y[/tex] ml of salt in 10% saline. There are [tex]0.12\cdot 50=6[/tex] ml of salt in 50 ml of 12% saline. Thus,
[tex]0.2x+0.1y=6[/tex]
15. We get the system of two equations:
[tex]\left\{\begin{array}{l}x+y=50\\0.2x+0.1y=6\end{array}\right.[/tex]
16. Solve this system. From the first equation:
[tex]x=50-y[/tex]
Substitute it into the second equation:
[tex]0.2(50-y)+0.1y=6\\ \\10-0.2y+0.1y=6\\ \\-0.1y=6-10\\ \\-0.1y=-4\\ \\y=40\\ \\x=50-y=50-40=10[/tex]
