20x^2+1/16 = 15x+3/20
20x^2+1/16 *5/5 = 15x+3/20 *4/4
100x^2+5/80= (15x+3)*4/80
100x^2+5/80 = 60x+12/80
100x^2+5= 60x+12
100x^2+5-60=12
100x^2-60x-7=0
D = (-60)^2*4*100*(-7) = 6400
x1 = -60+-80/200 = x1=-0.1 x2=0.7
=> Otvet: x1 = -1/10 = -0.1
x2= 7/10 = 0.7