Answer:
21 mails
Step-by-step explanation:
Let there are x no of texts and y no of emails.
Condition 1,
x+y = 20 ...(1)
Condition,
x=2y-1 ...(2)
Put the value of x from equation (2) in (1). So,
(2y-1)+y = 20
Taking like terms together,
2y-y=20+1
y=21
So, Devin sent 21 mails,.
Answer:

Step-by-step explanation:
Given

Required
Find n
Simplify (n + 1)!

Factorize
![n![2(n+1) + 6] = 3(n+1)*n!](https://tex.z-dn.net/?f=n%21%5B2%28n%2B1%29%20%2B%206%5D%20%3D%203%28n%2B1%29%2An%21)
Divide both sides by n!

Open brackets


Collect like terms


Multiply both sides by -1

Answer:
△ABC is congruent to △DEF
Step-by-step explanation:
△DEF is a reflection of △ABC across the y-axis. (Each x-coordinate is negated.)
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<em>Comment on presentation</em>
This would be much easier to answer if you would use a conventional representation of ordered pairs:
... (-1, -2) instead of "begin ordered pair negative 1 comma negative 2 end ordered pair"
The surface area of the prism would be 64 inch^{2}.