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9x-4y=2000, 7x-3y=2000

Solve the first given equation for y.
1. 9x - 4y = 7x - 3y
2. 2x = y

Sbstitute y into equation 1.
3. 9x - 4(2x) = 2000
4. 9x - 8x = 2000
5. x = 2000   <<<<<

Substitute x into equation the second given equation.
6. 7(2000) - 3y = 2000
7. 7(2000) - 2000 = 3y
8. 6(2000) = 3y
9. 2(2000) = y
10. y = 4000    <<<<<

Substitute both x and y into the first given equation.
11. 9(2000) - 4(4000) = 2000
12. 18000 - 16000 = 2000
13. 2000 = 2000

Substitute both x and y into the second given equation.
14. 7(2000) - 3(4000) = 2000
15. 14000 - 12000 = 2000
16. 2000 = 2000
by Level 11 User (78.4k points)
Answer:- x = 2000 y = 4000 Explanation

: - Given pair of linear equations

9x - 4y = 2000 ---eq (1)

7x - 3y = 2000---eq (2)

LCM of coefficients of y i.e. 4 and 3 is 12 So Multiply eq (1) with 3 and eq (2) with 4 After multipliplying pair of linear equation we have

27x - 12y = 6000 ---eq (3)

28x - 12y = 8000 ---eq (4)

Subtracting eq (2) from eq (1)

⇒ 27x - 12y - (28x - 12y) = 6000 - 8000

⇒ 27x - 12y - 28x + 12y = - 2000

⇒ - x = - 2000

⇒ x = 2000 Substitute x = 2000 in eq (1)

⇒ 9x - 4y = 2000

⇒ 9(2000) - 4y = 2000 ⇒ 18000 - 4y = 2000

⇒ 18000 - 2000 = 4y

⇒ 16000 = 4y

⇒ 16000/4 = y ⇒ 4000 = y

⇒ y = 4000 ∴ x = 2000 and y = 4000

Note: - The method used to solve this question is ELIMINATION METHOD.
by

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