Answer:
and 
Step-by-step explanation:
Let
x -----> the number of polyphonic ringtones
y ----> the number of standard ringtones
we know that
-----> equation A
-----> equation B
Solve the system of equations by substitution
Substitute equation A in equation B and solve for y





Find the value of x
Answer:
Step-by-step explanation:

Answer:
615.44 would be the answer
Step 2: She did not simplify under the square root correctly
under the square root:
(-6)^2 =36
and -4(5)(-8) =160
therefore under the square root it needs to be square root of 36+160 which is square root of 196.
That answer is 14 when square rooted
The rule of geometric sequence is ⇒⇒⇒ a * r^(n-1)
Where a is the first term and r is the common ratio
for the given sequence √5 , √10 , 2√5 , .......
a = √5
r = √10 / √5 = √2
The ninth term = √5 * (√2)^(9-1) = √5 * (√2)⁸ = 16 √5
the correct answer is the third option 16√5