Bonjour,
x + y = 5
2x - 14 = 0
x + y = 5
2(x - 7) = 0
x + y = 5
x - 7 = 0
x + y = 5
x = 7
y + 7 = 5
x = 7
y = -2
x = 7
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4x - 3y = 11
y - 2 = 9
4x - 3y = 11
y = 9 + 2
4x - 3y = 11
y = 11
4x - 3 × 11 = 11
y = 11
4x - 33 = 11
y = 11
4x = 44
y = 11
x = 11
y = 11
