Question

3. Solve the following pair of linear equations using a method of your choice
20x + 80y = 180 and 80x + 20y = 120

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Answer 1

Answer:

x=10; y=2

Step-by-step explanation:

x=180-80y/20

put this value of x in second eq.

80×180-80y/20+20y=120

after solving it we get

720-320y+ 20y=120

720-300y=120

-300y=120-720

-300y=-600

y=-600÷ -300

y=2

put the value of y in any of these equations

after solving you will find

x=10

Answer 2

Answer:

x=1, y=2

Step-by-step explanation:

2ox+80y=180.........(1)

80x+20y=120.........(2)

adding equation (1)&(2)

20x+80y=180

+

80x+20y=120

100x+100y=300........(divide by 100)

x+y=3......(3)

subtract equations(1)&(2)

20x+80y=180d

-

80x+20y=120

- - -

-60x+60y=60..........(divide by 60)

-x+y=1...........(4)

adding equation (3)&(4)

x+y=3

+

-x+y=1

2y=4

y=4/2

y=2

y=2 put the value in equation (3)

x+y=3

x+2=3

x=3-2

x=1

x=1, y=2