Question

x-8y=70 and 3x-7y=57 solve in substitution and elimination method​

Answer 1

Question

x-8y=70 ------------------------Equation 1

3x-7y=57------------------------Equation 2

Answer:

Substitution method

From eq 1 we get x = 70+8y

We substitute this value of x in eq 2,

3(70+8y) - 7y = 57

210 + 24y - 7y = 57

24y - 7y = 57 - 210

17y = -153

y = -153/17

y = -9

Now we can get the value of x by substituting the value of y in eq 1,

x - 8(-9) = 70

x + 72 = 70

x = 70 - 72

x = -2

Therefore , x = -2     and       y = -9

Elimination method

x-8y=70 ------------------------Equation 1(Multiply by 3)

3x-7y=57------------------------Equation 2(Multiply by 1)

We get,

3x - 24y = 210

3x - 7y = 57

Now change signs,

3x - 24y = 210

-3x + 7y = -57

-17y = 153

y = -9

We can get value of x by substituting the value of y in eq 1,

x - 8(-9) = 70

x + 72 = 70

x = 70 - 72

x = -2

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Answer 2

Answer:

(-2,-9)

Step-by-step explanation:

Given simultaneous equations

x - 8y = 70 ..............(1)

3x - 7y = 57 ............(2)

1) Substitution Method.

From equation (1), x = 8y + 70

Substituting this in (2) we get

3(8y + 70) -7y = 57

or 24y + 210 - 7y = 57

or 17y = -210+57 = -153

or y = -153/17 = -9

Using y = -9 in x = 8y + 70 we get

x = 8*(-9) + 70

or x = -72 + 70

or x = -2

Hence (x,y) = (-2,-9)

2) Elimination Method

Multiplying both side of (1) by 3 we get

3x - 24y = 210 ..........(3)

Substracting (3) from (2),we get(In this step we are eliminating the variable x)

(3x-7y)-(3x-24y) = 57-210

or 3x-7y-3x+24y = -153

or 24y - 7y = -153

or 17y = -153

or y = -153/17 = -9

Substituting value of y in (1) we get

x - 8*(-9) = 70

or x + 72 = 70

or x = 70-72

or x = -2

Hence (x, y) = (-2, -9)