x - 3y = 1 ⇒ 3x - 9y = 3
3x - 5y = 11 ⇒ 3x + 5y = 11
-14y = -8
-14 -14
y = ⁴/₇
x - 3y = 1
⁴/₇ - 3y = 1
- ⁴/₇ - ⁴/₇
-3y = ³/₇
-3 -3
y = ⁻¹/₇
(x, y) = (⁴/₇, ⁻¹/₇)
None But, 80 x 2 = 160 and 80 + 2 = 82, are you sure you mean 92?
The answer i got when i worked it out with my math teacher was C
Answer:
Step-by-step explanation:
1) Let the random time variable, X = 45min; mean, ∪ = 30min; standard deviation, α = 15min
By comparing P(0 ≤ Z ≤ 30)
P(Z ≤ X - ∪/α) = P(Z ≤ 45 - 30/15) = P( Z ≤ 1)
Using Table
P(0 ≤ Z ≤ 1) = 0.3413
P(Z > 1) = (0.5 - 0.3413) = 0.1537
∴ P(Z > 45) = 0.1537
2) By compering (0 ≤ Z ≤ 15) ( that is 4:15pm)
P(Z ≤ 15 - 30/15) = P(Z ≤ -1)
Using Table
P(-1 ≤ Z ≤ 0) = 0.3413
P(Z < 1) = (0.5 - 0.3413) = 0.1587
∴ P(Z < 15) = 0.1587
3) By comparing P(0 ≤ Z ≤ 60) (that is for 5:00pm)
P(Z ≤ 60 - 30/15) = P(Z ≤ 2)
Using Table
P(0 ≤ Z ≤ 1) = 0.4772
P(Z > 1) = (0.5 - 0.4772) = 0.0228
∴ P(Z > 60) = 0.0228
y= 1.25x+6.75
Make 31.75 y because that is the total cost he paid.
1.25x+6.75=31.75
1.25x=25
x=20
So he had 20 refills.
