X representa o numero das suas respostas certas.
y represnta o numero das suas respostas erradas.
O total de perguntas <span>é 25, portanto
x + y = 25
Agora tratamos do dinheiro.
Come</span>ça com <span>R$ 500,00
Pelas x respostas certas, recebe 200x.
Pelas y respostas errads perde 150y.
O total de dineheiro inicial mais os ganhos menos as perdas s</span>ão iguais a
R$ 600,00, portanto
500 + 200x - 150y = 600
200x - 150y = 100
20x - 15y = 10
Temos um sistema de duas equações com duas variaveis.
<span>x + y = 25</span>
20x - 15y = 10
15x + 15y = 375
+ 20x - 15y = 10
---------------------------
35x = 385
x = 11
x + y = 25
11 + y = 25
y = 14
Resposta: Errou 14 perguntas.
Step-by-step explanation:
Consider the provided information.
For the condition statement
or equivalent "If p then q"
The rule for Contrapositive is: Negative both statements and interchange them. 
Part (A) If you are taller than 6 ft, then it is unpleasant for you to travel in economy class.
Here p is "you are taller than 6 ft, and q is "it is unpleasant for you to travel in economy class".
It is given that Your contrapositive must not contain explicit references to negation. Assume that the negation of "unpleasant" is "pleasant".
Contrapositive: If it is pleasant for you to travel in economy class then you are not taller than 6 ft then.
Part (B) "If x ≥ 0 and y ≥ 0 then xy ≥ 0" where x, y are real numbers.
Here p is "xy≥ 0, and q is "x ≥ 0 and y ≥ 0"
The negative of xy≥ 0 is xy<0, x ≥ 0 is x<0 and y ≥ 0 is y<0.
Remember negative means opposite.
Contrapositive: If xy < 0 then x<0 and y<0.
The ratio of the distance between the foci and the length of the <em>major</em> axis is called eccentricity.
<h3>
Definitions of dimensions in ellipses</h3>
Dimensionally speaking, an ellipse is characterized by three variables:
- Length of the <em>major</em> semiaxis (
). - Length of the <em>minor</em> semiaxis (
). - Distance between the foci and the center of the ellipse (
).
And there is the following relationship:
(1)
Another variable that measure how "similar" is an ellipse to a circle is the eccentricity (
), which is defined by the following formula:
,
(2)
The greater the eccentricity, the more similar the ellipse to a circle.
Therefore, the ratio of the distance between the foci and the length of the <em>major</em> axis is called eccentricity. 
To learn more on ellipses, we kindly invite to check this verified question: brainly.com/question/19507943
Answer:
30 seconds
Step-by-step explanation:
→ Work out how many floors it's going to travel
15 - 3 = 12 floors
→ Work out how many meters 12 floors is
12 × 5 = 60 meters
→ Work out how long that will take
60 ÷ 2 = 30 seconds