Ann wants to choose from two telephone plans. Plan A involves a fixed charge of $10 per month and call charges at $0.10 per minute. Plan B involves a fixed charge of $15 per month and call charges at $0.08 per minute.
Plan A $10 + .10/minute
Plan B $15 + .08/minute
If 250 minutes are used:
Plan A: $10+$25=$35
Plan B: $15+$20=$35
If 400 minutes are used:
Plan A: $10+$40=$50
Plan B: $15+$32=$47
B is the correct answer. How to test it:
Plan A: $10+(.10*249 minutes)
$10+$24.9=$34.9
Plan B: $15+(.08*249 minutes)
$15+$19.92=$34.92
Plan A < Plan B if less than 250 minutes are used.
Answer:

Step-by-step explanation:



Substitute
into second equation:




Substitute
and
into the third equation:



Substitute
into
:

Plug in y and z values into
:

Answer:
? = 4.29
Step-by-step explanation:
Remark
Let x be the question mark. You get the proportionality by using the dimensions of the little triangle to the dimensions of the large triangle.
Equation
14/(14+ 4) = 15/(x + 15) Combine like terms on the left
14/18 = 15/(x + 15) Cross multiply
14*(x + 15) = 18 * 15 Simplify the right
14(x + 15) = 270 Divide by 14
x + 15 = 270 / 14
x + 15 = 19.29 Subtract 15 from both sides
x = 19.29 - 15
x = 4.29
We first obtain the equation of the lines bounding R.
For the line with points (0, 0) and (8, 1), the equation is given by:

For the line with points (0, 0) and (1, 8), the equation is given by:

For the line with points (8, 1) and (1, 8), the equation is given by:

The Jacobian determinant is given by

The integrand x - 3y is transformed as 8u + v - 3(u + 8v) = 8u + v - 3u - 24v = 5u - 23v
Therefore, the integration is given by: