Let

be the number of rides Chandler takes in a month. Then the cost with the MetroCard is still $81, but the cost without the MetroCard is

. So we can set up an equation representing what we want: "The cost with a MetroCard of r rides in a month is less than the cost without a MetroCard." In equations,

Thus, at a minimum, Chandler must take 41 rides for his MetroCard to be cheaper than not having it.
Okay, so first, the quadrants on a coordinate plane go counter clockwise.
2 | 1
__________|__________
3 | 4
(1/2, -1.8) Would be a little to the right of the y axis, and a little below the x axis.
So, your answer would be D) Quadrant IV
60=5k is the answer for your question
Since measure REU equal measure SFT, RE=FT and SF=EU then the two triangles REU et SFT are similar.
Then we deduce that the two sides RU and ST are equal, RU=ST.
Also, since the two triangles above are similar, then the two angles FST and RUE are equal. We deduce that the two lines RU and ST are parallel (interior opposite angles principles.)
We have two facts now:
RU = ST and RU parallel to ST, we deduce that the quadrilateral is a parallelogram.