3x - 5y = 21....multiply by 2
-7x + 2y = 4 ..multiply by 5
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6x - 10y = 42 (result of multiplying by 2)
-35x + 10y = 20 (result of multiplying by 5)
----------------add
- 29x = 62
x = -62/29
2y = 7x + 4
2y = 7(-62/29) + 4
2y = -434/29 + 4
2y = -434/29 + 116/29
2y = -318/29
y = -318/29 * 1/2
y = -318/58
y = -159/29
solution is (-62/29, -159/29)
