y = 5 Explanation: I would multiply the first equation by − 4 and the second by 3 and add together the two equatins (in columns): { − 12 x − 28 y = − 104
{ 12 x + 15 y = 39
0 − 13 y = − 65
So: y = 65 13 = 5
Substitute back this value into the first equation: 3 x + 7 ⋅ 5 = 26