Answer:
x must equal 5 and y must equal 2
therefore,
5a + 2b = 23 and
5a - 2b = 7.
I'm gonna take 5a + 2b = 23 and add 7 to each side:
5a + 2b + 7 = 30
and substitute 5a -2b in for 7 on the left side:
5a + 2b + (5a-2b) = 30
10a = 30
a = 3
Now we know a. Now take
5a -2b = 7
and substitute in 3 for a
5*(3) - 2b = 7
15 -2b = 7
8 = 2b
b = 4
a = 3 and b = 4
Step-by-step explanation:
Answer:
1, 2, 6
Step-by-step explanation:
The z score shows by how many standard deviations the raw score is above or below the mean. The z score is given by:

Given that mean (μ) = 130 texts, standard deviation (σ) = 20 texts
1) For x < 90:

From the normal distribution table, P(x < 90) = P(z < -2) = 0.0228 = 2.28%
Option 1 is correct
2) For x > 130:

From the normal distribution table, P(x > 130) = P(z > 0) = 1 - P(z < 0) = 1 - 0.5 = 50%
Option 2 is correct
3) For x > 190:

From the normal distribution table, P(x > 3) = P(z > 3) = 1 - P(z < 3) = 1 - 0.9987 = 0.0013 = 0.13%
Option 3 is incorrect
4) For x < 130:

For x > 100:

From the normal table, P(100 < x < 130) = P(-1.5 < z < 0) = P(z < 0) - P(z < 1.5) = 0.5 - 0.0668 = 0.9332 = 93.32%
Option 4 is incorrect
5) For x = 130:

Option 5 is incorrect
6) For x = 130:

Since 1.5 is between 1 and 2, option 6 is correct
2+2 is 4 - 1 is 3 QUICK MATHS