Answer:
Maybe -3
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.
Given parameters:
Midpoint of AB = M(3, -1)
Coordinates of A = (5,1)
Unknown:
Coordinates of B = ?
Solution:
To find the mid point of any line, we use the expression below;
and 
where
and
= coordinates of the mid points = 3 and -1
x₁ = 5 and y₁ = 1
x₂ = ? and y₂ = ?
Now let us input the variables and solve,
3 =
and -1 = 
5 + x₂ = 6 -2 = 1 + y₂
x₂ = 1 y₂ = -2 -1 = -3
The coordinates of B = 1, -3
Finding the slope, you get (-1-(-5))/(3-0)=4/3. For finding the slope, you can also just count the rise and the run, then divide them. For exampe, (3,-1) is 4 units higher and 3 units to the left, so the slope is 4/3. Also, looking at the graph shows you that the y-intercept is just (0,-5).
It's +44 and -6
44-(-6)= 50
44 + (-6)= 38