Thread: I need to find the solution of the system. There are 3 problems.

Hello, and thank you for your help. I have been doing this all day, and I cannot get the right answer for the life of me. All other 70 questions I was able to solve. Somehow I am missing it on these. Please show me how you did your work. I do not have to show the work, but I would like to learn and see what I did wrong. God bless.

1. 0.05X + 0.25Y = 66
0.15X + 0.05Y = 72

2. 0.3X - 0.2Y = 4
0.5X + 0.3Y = 1

3. 9x-9y = 9
7y-3x = -5

Originally Posted by OneidaFL

Hello, and thank you for your help. I have been doing this all day, and I cannot get the right answer for the life of me. All other 70 questions I was able to solve. Somehow I am missing it on these. Please show me how you did your work. I do not have to show the work, but I would like to learn and see what I did wrong. God bless.

1. 0.05X + 0.25Y = 66
0.15X + 0.05Y = 72

2. 0.3X - 0.2Y = 4
0.5X + 0.3Y = 1

3. 9x-9y = 9
7y-3x = -5

Dear OneidaFL,

Let us try the first one,

Now,



Simplify and you can get the answer for Y. Then you can find X by substituting Y in one of the two equations. The same method applies for all the other questions as well. Hope you will be able to continue.

Originally Posted by OneidaFL

1. 0.05X + 0.25Y = 66
0.15X + 0.05Y = 72

Multiply by 100 to get rid of decimal points:
5x + 25y = 6600
15x + 5y = 7200
Divide by 5 to simplify:
x + 5y = 1320 [1]
3x + y = 1440 [2]

From [2]: y = 1440 - 3x
Substitute that in [1]

OK?

Others can be solved similarly.