Hmmmmmm I think I know the answer to this
One way to carry out this problem is to simply take the value that you already know, which is that 1/5 is 20 % and multiply it by 2 for 2/5 or 2 (1/5ths) and do this for all of them. There is a pattern that occurs for every increase in one out of denominator of 5.
Let
be the volume of 20% solution,
the volume of the 60% solution. We want a total volume of 400 mL in the final mixture, so

Each mL of either solution will contribute a corresponding concentration, and in the final mixture we want the 400 mL to have a 40% concentration, which means we should also have

Solve the system and we get
.
Answer:
-1
Step-by-step explanation:
We can plug in -3 for x and solve:
f(-3) = -3 + 2
= -1
Inequality: 20+40n≤260
Graphing inequality is in the picture I posted.