Question

How to solve this system of equation 3x + y= 17 and 4x + 2 y = 20

Answer 1

3x + y= 17        (a)
4x + 2 y = 20    (b)

Multiply (a) by 2:

6x + 2y = 34   (a)
4x + 2y = 20   (b)

make:   (a) - (b)

2x = 14 -----> x =7

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Replace the value of x = 7 in one of anterior equation:

3x + y= 17  
3 x 7 + y = 17
21 + y = 17
y = 17 - 21
y = -4