Answer:
Ella gastó 12 dólares y le quedan 20 dólares.
There are 18 terms are in her series
<h3>What is Arithmetic progression series?</h3>
Arithmetic Progression (AP) is a sequence of numbers in order in which the difference of any two consecutive numbers is a constant value.
Given that: t(n) = −9 + 21n=l
a= 12, Sum = 3429
As, Sum of series =3429
n/2 (a+l) =3429
n/2 (12 +21n-9)= 3429
n/2 (3+21n)=3429
21n² + 3n= 6858
21n² + 3n- 6858=0
7n² + n- 2286=0
For solving for n, get
n= 18 or n= -127/7
Thus, there 18 terms in the series.
Learn more about series here:
brainly.com/question/12146981
#SPJ1
Answer: x = 13
Step-by-step explanation: When solving an equation like this, we are trying to get our variable which is our letter by itself.
So we first want to ask ourselves what is the 14 doing to <em>x</em>. Well, we can see that it's being added to <em>x</em> so to get <em>x</em> by itself, we will do the opposite of addition which is subtraction. So we subtract 14 from both sides of the equation.
The +14 -14 cancels out so we're left with <em>x</em> on the left.
On the right, we must subtract 14 from 27 to get 13.
So we have x = 13 which is the solution to this equation.