Math Help!
posted by Rana on .
1.) Solve the system by graphing. You may use paper or a calculator.
2x  y = 8
x + 3y = 11
2.) The revenue for a certain brand of toothpaste is y = 2.5x where 'x' is the number of tubes of toothpaste sold and 'y' is the total income for selling 'x' tubes. The cost equation is y = 0.9x + 3000, where 'x' is the number of tubes manufactured and 'y' is the cost of producing 'x' tubes. Find the value of 'x' where the company breaks even.
x=?
Please help, thank you!

1.)
Plot a Cartesian coordinate system
1 equation :
For x = 0
 y = 8 Multiply both sides by  1
y =  8
For y = 0
2 x = 8 Divide both sides by 2
x = 4
Mark points ( 0 ,  8 )
x = 0 , y = 8
and ( 4 , 0 )
x = 4 , y = 0
and draw line
2 equation:
For x = 0
3 y = 11 Divide both sides by 3
y = 11 / 3 = 3.67
For y = 0
x = 11
Mark points ( 0, 3.67 )
x = 0 , y = 3.67
and ( 11 , 0 )
x = 11 , y = 0
and draw line
Intersection of this two lines is solution of system.
x = 5 , y = 2
OR
2 x  y = 8
y = 2 x  8
x + 3y = 11
y = ( 11  x ) / 3
in google type :
functions graphs online
When you see list of resulrt click on :
Draw Function Graphs  Plotter  Rechneronline
When page be open in blue rectangle type:
2 x 8
in gray rectangle type:
( 11  x ) / 3
In options :
Range xaxis from set :
 3 to 7
Range yaxis from set:
 15 to 5
and click option draw
2.)
2.5 x = 0.9 x + 3000 Subtract 0.9 to both sides
2.5 x  0 . 9 = 0.9 x + 3000  0.9
1.6 x = 3000 Divide both sides by 1.6
x = 3000 / 1.6 = 1875 
0.9(7x+5)=1.6(x3)