21/2: 1 1/4+1 2/3*(-3/5)= 1/3*(-2/5): (-1/3)= -3 /12: (-2/5*1/3)=

1) 3/8 : 5/12 = 3/10 2) 3 1/2 • 2/5 = 7/2 • 2/5 = 7/5 3) 1 : 3 1/3 = 1 : 10/3 = 3/10 4) 3/10 - 7/5 + 3/10 = 6/10 - 14/10 = - 8/10 = - 4/5 ответ ( - 4/5 )