Question

if 5x+7y=40 and 7x+5y=20.find the value of x and y.​

Answer 1

5x +7y =40

7x + 5y =20

multiple eq1 by 7 and eq2 by 5

35x+49y=280

35x + 25y =100

now subtracting eq

35x+49y=280

35x+25y=100

we get 24y=180

y =180/24

y= 90/12=45/6=15/2

put value in eq1

5x+7y=40

5x+7×15/2=40

5x +105/2=40

5x = 40-105/2

5x = 80-105/2

5x =25/2

x =25/5×2

x = 5/2

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