Answer:
- The system of equations is x + y = 85 and 7/20x+2/5y=31
- To eliminate the x-variable from the equations, you can multiply the equation with the fractions by 20 and multiply the other equation by -7.
- B-She used 60 minutes for calling and 25 minutes for data.
Step-by-step explanation:
It is always a good idea to start by defining variables in such a problem. Here, we can let x represent the number of calling minutes, and y represent the number of data minutes. The the total number of minutes used is ...
x + y = 85
The total of charges is the sum of the products of charge per minute and minutes used:
7/20x + 2/5y = 31.00
We can eliminate the x-variable in these equations by multiplying the first by -7 and the second by 20, then adding the result.
-7(x +y) +20(7/20x +2/5y) = -7(85) +20(31)
-7x -7y +7x +8y = -595 +620 . . . . eliminate parentheses
y = 25 . . . . . . . . simplify
Then the value of x is
x = 85 -y = 85 -25
x = 60
<span>arc length = circumference • [central angle (degrees) ÷ 360]
Solving this equation for circumference:
</span>
<span>circumference = arc length / (central angle / 360)
</span><span>circumference = 12 / (85/360)
</span>circumference = 12 / <span><span>0.2361111111
</span>
</span>
<span>circumference =
</span>
<span>
<span>
<span>
50.8235294118
</span>
</span>
</span>
Source:
http://www.1728.org/radians.htm
This question is quite simple really. They are basically asking you to combine like terms. You have two different figures with the variable y, so you just combine the them. It would then be 3x + 2y. You cannot simplify this equation any further since there is nothing to solve for or anymore like terms to combine.
A and C is the answer
hope you'll learn from your teacher how?