7*c - 10*d - 6*c + 12*d
7*c - 10*d - 6*c + 12*d при c = 1/2
7*(1/2) - 10*d - 6*(1/2) + 12*d
7/2 - 10*d - 6/2 + 12*d
1/2 + 2*d
c + 2*d
1.0*c + 2.0*d
7*c + 12*d - 6*c - 10*d