Answer:
A book is worth $1 and a DVD is worth $12.
Step-by-step explanation:
The equations (2 unknowns and two equations, d is for a DVD and b is for a book):
For David: 3d+4b=40
For Anna: d+6b=18
Now multiply the second equation with -3 and add to the first equation:
3d+4b=40
−3d−18b=−54
Combined equation: −14b=−14 and b=1 (means that each book is worth $1).
Now for DVD price, use the second equation:
d=18−6 or d=12 (means that each DVD is worth $12).
A book is worth $1 and a DVD is worth $12.
Answer: -216
Step-by-step explanation:
To solve the exercise you must use the formula shown below:

Where:

You should find 
The formula to find it is:

Where d is the difference between two consecutive terms.

Then:

Substitute it into the first formula. Therefore, you obtain:

Answer:
Step-by-step explanation:
take x degree as reference angle
using tan rule
tan x=opposite/adjacent
tan x=6.1/5.1
tan x=1.19
x=
1.19
x=49.95
x=50 degree
He won about 25% because 6/12 would be 1/2 and 3 is 1/2 of 6 or a 1/4 so 25%
Some examples of geometric constraints include parallelism, perpendicularity, concentricity and symmetry. Parallelism occurs when two or more lines or axes of curves are equidistant from each other. Perpendicularity is a constraint in which lines or axes of curves intersect at right angles.