The answer would be 5,400 ( 3000 times 0.15 would be 450 then, 450 times 12 is 5,400.)
Answer:
3/4
Step-by-step explanation:
1/3 + 1/4 + 1/6
notice that the denominators consists of the numbers 3, 4 and 6 and that the lowest common multiple for all 3 numbers is 12, hence all these fractions can be expressed with a denominator of 12
i.e
1/3 = 4/12
1/4 = 3/12
1/6 = 2/12
hence,
1/3 + 1/4 + 1/6
= 4/12 + 3/12 + 2/12
= (4+3+2) / 12
= 9/12 (simply)
= 3/4
Solution:
Let x represent a number of calling minutes. According to the problem, we want:

now, putting the similar terms together, we obtain:

this is equivalent to:

now, solving for x, we get:

then, the correct answer for the first question is:
400 minutes is the number of minutes the two plans cost the same
now, for the second question, we can replace the above value (400 minutes) into the following equation:

so that, the correct answer for the second question is:
$55 is the cost when the two plans cost the same
let's firstly find the equation of the parabola, bearing in mind that x-intercepts or solutions/zeros/roots means y = 0.
![\bf ~~~~~~\textit{vertical parabola vertex form} \\\\ y=a(x- h)^2+ k\qquad \begin{cases} \stackrel{vertex}{(h,k)} \end{cases} \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ \begin{cases} h=1\\ k=-9 \end{cases}\implies y=a(x-1)^2-9 \\\\\\ \textit{we also know that } \begin{cases} x=0\\ y=-6 \end{cases}\implies -6=a(0-1)^2-9\implies 3=a(-1)^2](https://tex.z-dn.net/?f=%5Cbf%20~~~~~~%5Ctextit%7Bvertical%20parabola%20vertex%20form%7D%20%5C%5C%5C%5C%20y%3Da%28x-%20h%29%5E2%2B%20k%5Cqquad%20%5Cbegin%7Bcases%7D%20%5Cstackrel%7Bvertex%7D%7B%28h%2Ck%29%7D%20%5Cend%7Bcases%7D%20%5C%5C%5C%5C%5B-0.35em%5D%20%5Crule%7B34em%7D%7B0.25pt%7D%5C%5C%5C%5C%20%5Cbegin%7Bcases%7D%20h%3D1%5C%5C%20k%3D-9%20%5Cend%7Bcases%7D%5Cimplies%20y%3Da%28x-1%29%5E2-9%20%5C%5C%5C%5C%5C%5C%20%5Ctextit%7Bwe%20also%20know%20that%20%7D%20%5Cbegin%7Bcases%7D%20x%3D0%5C%5C%20y%3D-6%20%5Cend%7Bcases%7D%5Cimplies%20-6%3Da%280-1%29%5E2-9%5Cimplies%203%3Da%28-1%29%5E2)
![\bf 3=a\qquad \qquad \textit{therefore}\qquad \qquad \boxed{y=3(x-1)^2-9} \\\\[-0.35em] ~\dotfill\\\\ \stackrel{y}{0}=3(x-1)^2-9\implies 9=3(x-1)^2\implies \cfrac{9}{3}=(x-1)^2\implies 3=(x-1)^2 \\\\\\ \pm\sqrt{3}=x-1\implies \pm\sqrt{3}+1=x\implies x= \begin{cases} \sqrt{3}+1\\ -\sqrt{3}+1 \end{cases}\implies x\approx \begin{cases} 2.73\\ -0.73 \end{cases}](https://tex.z-dn.net/?f=%5Cbf%203%3Da%5Cqquad%20%5Cqquad%20%5Ctextit%7Btherefore%7D%5Cqquad%20%5Cqquad%20%5Cboxed%7By%3D3%28x-1%29%5E2-9%7D%20%5C%5C%5C%5C%5B-0.35em%5D%20~%5Cdotfill%5C%5C%5C%5C%20%5Cstackrel%7By%7D%7B0%7D%3D3%28x-1%29%5E2-9%5Cimplies%209%3D3%28x-1%29%5E2%5Cimplies%20%5Ccfrac%7B9%7D%7B3%7D%3D%28x-1%29%5E2%5Cimplies%203%3D%28x-1%29%5E2%20%5C%5C%5C%5C%5C%5C%20%5Cpm%5Csqrt%7B3%7D%3Dx-1%5Cimplies%20%5Cpm%5Csqrt%7B3%7D%2B1%3Dx%5Cimplies%20x%3D%20%5Cbegin%7Bcases%7D%20%5Csqrt%7B3%7D%2B1%5C%5C%20-%5Csqrt%7B3%7D%2B1%20%5Cend%7Bcases%7D%5Cimplies%20x%5Capprox%20%5Cbegin%7Bcases%7D%202.73%5C%5C%20-0.73%20%5Cend%7Bcases%7D)