Answer:
D. x+2x+x+10
Step-by-step explanation:
Answer:
D. An example that shows a statement is not true.
Step-by-step explanation:
Let 
be the number of liters of the 10% solution to be used, and 
the number of liters of the 4% solution. The chemist wants to end up with a 4 liter solution, so
For each liter used in the mixture, a concentration of either 10% or 4% acid will be contributed, and the goal is to make a 4L solution whose concentration is 7%, which means
Solving for 
gives 
, so 2L of both solutions is needed.
Answer: 7c + 2
Step-by-step explanation:
Combine like terms hope this helps
