How do I do these Algebra problems?

Question

1) 720x+1440y=6480

x+1.25y=6

2) 4.25x+5.50y=25

x+y=5

Answer 1

1) x=1 y=4

2) x=2 y=3

Answer 2

x=6-1.25y

720(6-1.25y)+1440y=6480

4320+540y=6480

540y=2160

y=4

x+1.25(4)=6

x+5=6

x=1

x=5-y

4.25(5-y)+5.50y=25

21.25-4.25y+5.50y=25

1.25y=3.75

y=3

x=2

Answer 3

hai friend you add first two terms &second term further divide then terms

Answer 4

*  720x=6480 - 1440y  <--- subtracted 1440y to iso the x

(720x)/ 720= (6480 - 1440y)/720 <---dividing by 720

x=(9 - 2y)    <-----now take this and substitute it in the bottom equation like this:

9 - 2y+1.25y=6  <-----iso y

-.75y= -3 <-------------/

y= 4    <-----------/

720x 1440(4)=6480  <-----------now put it back in first problem and sovle for x  (x= 1, y=4)

Answer 5

720x+1440y=6480    eq. 1

x+1.25y=6    eq. 2

from eq. 2:  x + 1.25y = 6

                    x = 6 - 1.25y

substitute in eq. 1:

720(6 - 1.25y) + 1440y = 6480

4320 - 900y = 1440y = 6480

- 900y - 1440y = 6480 - 4320

-2340y = 2160

y = 2160/-2340

y = 12/13      ANSWER

Therefore,

x = 6 - 1.25y

x = 6 - 1.25(12/13)

x = 63/13    ANSWER

2) 4.25x+5.50y=25       eq. 1

                    x+y=5         eq. 2

Multiply eq. 2 by - 4.25 and then add the result

to eq. 1:

    4.25x  + 5.50y = 25

  - 4.25x   - 4.25y = - 21.25

  ____________________

                   1.25y = 3.75

                           y = 3.75/1.25

                           y = 3     ANSWER

Therefore, from eq. 2:

x + 3 = 5

x = 5 - 3

x = 2    ANSWER

Hope this helps.

teddy boy

Answer 6

Combine like terms and then solve like an equation?

Answer 7

1) 720x + 1440y=6480

   x + 2y = 9(divide by 720 to simplify the equation)

   x+1.25y=6

now subtract 2nd eqn from the 1st one.

  2y-1.25y=9-6

   0.75y=3

y=4

x+2*4=9

x=1

DO THE 2ND PROBLEM IN THE SAME MANNER

- nandu