Answer:
5 hours
Step-by-step explanation:
Let s and w represent hours spent traveling south and west, respectively. The problem statement tells us ...
s + w = 8 . . . . . . total trip time
344s + 351w = 2773 . . . . total mileage (using d = s·t)
By Cramer's rule, we can find the value of s as ...
s = (1(2773) -351(8))/(1(344) -351(1)) = -35/-7 = 5
The plane was heading south for 5 hours.
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<em>Comment on Cramer's rule</em>
For the equations ...
ax +by = c
dx +ey = f
The solution for x can be found to be ...
x = (bf-ec)/(bd-ea)
Similarly, the solution for y is ...
y = (cd-fa)/(bd-ea)
<span>10x + 30(2) = 20(x + 2)
10x + 60 = 20x + 40
10x = 20
answer
x = 2 liters
So you would need 2 liters of the 10% solution to make the 30% solution 20%.</span>
58 books can be expected to be turned in overdue
