# Simultaneous Equation challenge.?

4x + y = 25

x - 3y = 16

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- Old Science GuyLv 75 years agoFavourite answer
...

4x + y = 25

x - 3y = 16

multiply 1st equation by 3

12x + 3y = 75

x - 3y = 16

now add them

13x = 91

x = 7

then

4x + y = 25

28 + y = 25

so

y = -3

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- JohnathanLv 75 years ago
4x + y = 25; y = 25 - 4x. Substitute for y in equation 2...

x - 3(25 - 4x) = 16

x - 75 + 12x = 16

13x - 75 = 16

13x = 91

x = 7. Substitute for x in equation 1...

4(7) + y = 25

28 + y = 25

y = -3.

The solution is (7, -3).

- lenpol7Lv 75 years ago
4x + y = 25

x - 3y = 16

Multiply the top eq'n by '3'

Hence

12x + 3y = 75

x - 3y = 16

Add

13x = 91

x = 7

When x = 7

4(7) + y = 25

28 + y = 25

y = -3

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