If the first 10 bricks come out at $ 4.5, I would be spending $ 45. The other 10 bricks come out at $ 3.5 so he would be spending $ 35. Therefore, he has $ 20 available to buy bricks at $ 2.5, which would be buying 8 additional bricks. Thus, in total, with $ 100, 28 bricks were purchased.
Answer: 
Step-by-step explanation:
We know that the standard quadratic equation is ax^2+bx+c=0
Let's compare all the given equation to it and , find discriminant.
1. a=2, b= -7, c=-9
So it has 2 real number solutions.
2. a=1, b=-4, c=4
So it has only 1 real number solution.
3. a=4, b=-3, c=-1
So it has 2 real number solutions.
4. a=1, b=-2, c=-8
So it has 2 real number solutions.
5. a=3, b=5, c=3
Thus it does not has real solutions.
Subtract the second equation from double the first equation:
2x+6y-2x-(-4y)=0
10y=0
Therefore, y=0. Substituting this into the first equation, we see that:
x+3(0)=3
x=3
Therefore, x=3. The solution to this system is x=3, y=0, or (3, 0).
U fill the tank at 1:45 a.m......then u wait 1 1/2 hrs....
1:45 + 1 hr = 2:45.....2:45 + 30 minutes (because 1/2 hr = 30 minutes) =
3:15.....so u remove the liquid at 3:15 a.m.
