Answer:
15.

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

There are
ml of salt in x ml of 20% saline and
ml of salt in 10% saline. There are
ml of salt in 50 ml of 12% saline. Thus,

15. We get the system of two equations:

16. Solve this system. From the first equation:

Substitute it into the second equation:

Answer: subtract 5 from both sides
Explanation: get rid of the 5 before moving on to isolating the variable
Answer:
9/7
Step-by-step explanation:
13/14 - 1/7 + 1/2
taking LCM
=(13-2+7)/14
=18/14
to its lowest term
=9/7
Answer: It is Geometric.
Step-by-step explanation: Because it does not have a fixed pattern that adds or subtract which arithmetic does.