>>128
#include <stdio.h>

int main(void)
{
double ma[3][4] = {{2, 4, 6, 6},
{3, 8, 7, 15},
{5, 7, 21, 24},
};
double p, d;
int i, j, k;

for (k = 0; k < 3; k++) {
p = ma[k][k];
for (j = k; j < 4; j++)
ma[k][j] /= p;
for (i = 0; i < 3; i++)
if (i != k) {
d = ma[i][k];
for (j = k; j < 4; j++)
ma[i][j] -= d * ma[k][j];
}
}

for (k = 0; k < 3; k++)
printf("x%d=%f\n", k + 1, ma[k][3]);

return 0;
}