Б) (30-1)(30+1) = (30²-1²) = 900-1 = 899
в) (60-1)(60+1) = (60²-1²) = 3600-1 = 3599
г) (100-1)(100+1) = (100²-1²) = 10000 - 1 = 9999
д) (20-2)(20+2) = (20²-2²) = 400-4 = 396
е) (50-2)(50+2) = (50²-2²) = 2500-4 = 2496
-31=31
50=50
-1 5/6= 1 5/6
-0,87=0,87
100=100
1 1/2 + 1 4/5 + х/3 = 43/100
х/3 = (150 + 180 + 43)/100
х/3 = 373/100
100х= 373*3
100х=1119
х=11,19