uv1.xy = 0.590, 0.890  
uv2.xy = 0.590, 0.596  
uv3.xy = 0.853, 0.890

uv1.xy *=1.66667;
uv2.xy *=1.66667;
uv3.xy *=1.66667;

;I get
uv1.xy = 0.490, 0.989
uv2.xy = 0.490, 0.499
uv3.xy = 0.931, 0.989
    

point scaling(point p,float sx,float sy) {
    point s;

    int c[1][3];
    int a[1][3]={p.x,p.y,1};
    int b[3][3]={sx,0,0,0,sy,0,0,0,1};

    multmat(a,b,c);//result in  с

    s.x=c[0][0];
    s.y=c[0][1];

    return s;
}