231,25*3-68+196=693,75-68+196=625.75+196=821.75
A3-b3=(a-b)(a2+ab+b2)
(a-b)/(a^1/3-b^1/3)=(a^1/3-b^1/3)(a^2/3+a^1/3b^1/3+b^2/3)/(a^1/3-b^1/3)=a^2/3+a^1/3b^1/3+b^2/3
1) 3/5-17/9=27/45-85/45=-58/45
2) 1/2-1/3= 3/6-2/6=1/6
3) 1/6:58/45=-29/135
4) 24-(-29/135)=23 135/135-(-29/135)=23 106/135
(238-149)+506=595
(48+16):(48-16)=2
(124+126)*(313-307)=1500
32*15-896:28 =448