Question

solve the following pairs of linear equations by the method of substitution, 7x-15y-20=0 and x+2y= 3​

Answer 1

Given Equations:-

• 7x - 15y - 20 = 0
• x + 2y = 3

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Need to find:-

• x = ?
• y = ?

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Method used:-

• Substitution

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Solution:-

7x - 15y - 20 = 0

→ 7x - 15y = 20

→ 7x = 20 + 15y

→ $\boxed{\purple{x = \dfrac{20 + 15y}{7}}}$

Substitute this value of x in 2nd equation:-

x + 2y = 3

→ $\dfrac{20 + 15y}{7} + 2y = 3$

→$\dfrac{20 + 15y + 14y}{7} = 3$

→$20 +29 y = 7 \times 3$

→ 29 y = 21 -20

→ - y = 1 ÷ 29

→ $\red{\boxed{\bold{\large{ y = 1/29}}}}$

Thus

x + 2y = 3

→ x + 2×( 1/29 )= 3

→ x + (2/29) = 3

→ x = 3 - 2/29

→ x =( 87 - 2) / 29

→ x = 85 / 29

→ $\red{\boxed{\bold{\large{ x = 85/29}}}}$

Answer 2

Step-by-step explanation:

7x-15y-20=0-------1

x+2y=3---------2

from 2 we get

x=3-2y

substitute this value in 1

7(3-2y)-15y-20=0

21-14y-15y-20=0

21-29y-20=0

1-29y=0

1=29y

y=1/29

put this value in 2 we get

x=3-2*1/29=87-2)/29=85/29