I am going over some math homework and need to know if I am getting the right answers.

1. Solving by elimination: 2x+3y=3, and 4x+6y=6 I say the determinant is o, there is no solution

2. y-11>2y-2
Is 1,-15,-17,-2 solutions: My answer = 1 is not, -15 is, -17 is, and -2 is not
3. 4x+9y=-2, and -4x+y=22
I am to solve and I say this is the answer: (-5, 2)
4. Soybean meal is 18% protein; cornmeal is 9% protein. How many pounds of each should be mixed together in order to get 360 pounds mixture is 11 % protein?
How many pounds of cornmeal should be in the mixture: Cornmeal=280 soybean =80
5. A cellular phone company offers a contract for which the cost c in dollars, of t minutes of telephone is given by c=0.25(t-400)+50.95 where it is assumed that t is greater than or equal to 400 minutes. What times will keep costs between 94.95 and 119.70
My answer: 576minutes and 675 minutes.
6. Solve: 5(r-7) +3>6(r+3)-22
My answer r<-28
7. Determine whether the ordered pair is a solution of the inequality
(-7, 5) x+y<-5: my answer is that it is a solution…-23<-5
8. Solve the graph 4x+14 is greater than or equal to 6 and -13 is greater than or equal to -7
After solving the graph it would be [2----------------5, 6,7,8,9
Did I get theses answers right?

#1, not so fast

Did you notice that the second equation is merely double the first one?
So you really have only one equation, which of course would have an infinite number of solutions
e.g. (0,1), (3,-1), (6,-3) ....

#2
y-11>2y-2
y - 2y > -2 + 11
- y > 9
y < -9
so your choices are correct

#3 All you had to do is sub in your answer into each equation to see if it works. It does!

#4
Again, just sub in to see if your values satisfy the conditions stated. They do

#5,6 yes

#7, no

x + y < -5 , for (-7,5)
-7 + 5 < -5
-2 < -5 ??, false

#8 ??? don't understand the question.