Givens
x + y = 3
x =6 - 4y
Solution
Use the top equation to substitute for x in the second equation.
x = 3 - y
Put this result into the second given equation and solve for y
3 - y = 6 - 4y Add 4y to both sides.
3 - y + 4y = 6 Combine on the left
3 + 3y = 6 Subtract 3 from both sides
3 - 3 + 3y = 6 - 3 Combine
3y = 3 Divide by 3
3y/3 = 3/3 Combine
y = 1
=========================
x + y = 3 but y = 1
x + 1 = 3 Subtract 1 from both sides.
x + 1 - 1 =3 - 1
x = 2
Answer
x = 2
y = 1
Answer:
The proportion of exam scores that are lower than Irina's score is 0.9938
Step-by-step explanation:
<u>Data</u>
- standard deviation (sd): 6 points
- value of interest (x): 95 points
z-score is computed as follows:
z = (x - mean)/sd
z = (95 - 80)/6 = 2.5
We want to find:
P(z < 2.5)
From the table attached:
P(z < 2.5) = 0.9938