Answer:
It's 20 Pounds btw.
Step-by-step explanation:
7+0.20x = 5+ 0.30x
x- number of additional pounds
In the figure below
1) Using the theorem of similar triangles (ΔBXY and ΔBAC),

Where

Thus,

thus, BC = 7.5
2) BX = 9, BA = 15, BY = 15, YC = y
In the above diagram,

Thus, from the theorem of similar triangles,

solving for y, we have

thus, YC = 10.
The answer should be (x-4)
Answer:
Given the system of equation:
......[1]
......[2]
we can rewrite equation [2] as;
......[3]
Substitute equation [3] into [1] to eliminate x, and solve for y;

Using distributive property: 

Combine like terms;
16 - 8y = -4
Add 4 to both sides we have;
20 - 8y = 0
Add 8y to both sides we have;
20 = 8y
Divide 8 to both sides we have;

Substitute the y-value in [3] we have;

x = 8 - 5 = 3
Therefore, the expression should be substituted into the first equation is,
and also the value of x = 3 and y = 2.5
N+23=19
-23 -23 Takeaway 23 from both sides
Answer is N= - 4