Найди сумму и разность дробей: а)6/7 и 0,3 б)17/20 и 0,7 в)5/9 и 0,4 г)3/5 и 0,2 д)13/25 е)2/13 и 0,07 ж)0,21 и 3/8 з)0,13 и 4/5 и)0,01 и 6/17

А) 6/7 + 0,3 = 6/7 + 3/10 = 60/70 + 21/70 = 81/70 = 1 11/70   6/7 - 0,3 = 6/7 - 3/10 = 60/70 - 21/70 = 39/70  б) 17/20 +0,7 = 17/20 + 7/10 = 17/20+14/20 = 31/20 = 1 11/20   17/20 - 0,7 = 17/20 - 7/10 = 17/20 - 14/20 = 3/20  в) 5/9 + 0,4 = 5/9 + 4/10 = 50/90 + 36/90 = 86/90 = 43/45   5/9 - 0,4 = 5/9 - 4/10 = 50/90 - 36/90 = 14/90 = 7/45 г) 3/5 + 0,2 = 3/5 + 2/10 = 6/10 + 2/10 = 8/10 = 4/5   3/5 - 0,2 = 3/5 - 2/10 = 6/10 - 2/10 = 4/10 = 2/5  д) 13/25 дописано е) 2/13 + 0,07 = 2/13 + 7/100 = 200/1300 + 91/1300 = 291/1300 2/13 - 0,07 = 2/13 - 7/100 = 200/1300 - 91/1300 = 109/1300 ж) 0,21 + 3/8 = 21/100 + 3/8 = 42/200 + 75/200 = 117/200   0,21 - 3/8 = 21/100 - 3/8 = 42/200 - 75/200 = -  33/200 з) 0,13 +  4/5 = 13/100 +4/5 = 13/100 + 80/100 = 93/100 0,13 - 4/5 = 13/100 - 4/5 = 13/100 -  80/100 = -  67/100 и) 0,01 + 6/17 = 1/100 +6/17 = 17/1700 + 600/1700 = 617/1700 0,01 - 6/17 = 1/100 -6/17 = 17/1700 - 600/1700 = -  583/1700

1) 3(a+2b)-a, a+3b=1.1= 3a + 6b - a = 2a + 6b = 2(a+3b) = 1.1 * 2 = 2,2 2) 2.4(3x+5y)-4y 0.9x+y=2= 7.2x + 12y - 4y = 7.2x + 8y = 8(0.9x + y) = 8 * 2 =16 3) 8(0.5a+3b)+8a a+2b=2.5= 4a + 24b + 8a = 12a + 24b = 12(a+2b) = 12 * 2.5 = 30 4) 3(0.6m+5n)-3n 0.3m+2n=4= 1.8m + 15n - 3n = 1.8m + 12n = 6(0.4, + 2n) = 6 * 4 = 24