а) 2,5-0,4* 3 1/3 = 21/10
б) 2 1/7*(3+6/3) = 75/7
a) 2 1/3-4:(3 2/5+9,8) = 5531/2499
б) (1/3+0,75):(2/3+5/12) = 1
l = 2*П*R = 2*П*0,6 = 1,2*П