simultaneous equations

Solve the following system:
{7 x + 4 y = 17 | (equation 1)
3 x + 4 y = 5 | (equation 2)
Subtract 3/7 × (equation 1) from equation 2:
{7 x + 4 y = 17 | (equation 1)
0 x+(16 y)/7 = (-16)/7 | (equation 2)
Multiply equation 2 by 7/16:
{7 x + 4 y = 17 | (equation 1)
0 x+y = -1 | (equation 2)
Subtract 4 × (equation 2) from equation 1:
{7 x+0 y = 21 | (equation 1)
0 x+y = -1 | (equation 2)
Divide equation 1 by 7:
{x+0 y = 3 | (equation 1)
0 x+y = -1 | (equation 2)
Collect results:
Answer: | x = 3         and          y = -1