2. 2/3 ÷ 1 7/9+ 55/84÷(43/63-25/36)= -53.1/2
1) 2. 2/3 ÷ 1 7/9 = 8/3 :16/9 = 8/3*9/16=3/2=1.1/2
2) 43/63-25/36 = 172/252 - 175/252=-3/252=-1/84
3) 55/84 : (-1/84) = -55/84 * 84= -55
4) 1.1/2 + (-55) = -54.2/2 +1.1/2 = -53.1/2
1.
66-45=21 21+45=66
2.
66+45=111 111-45=66
3.
200+49-120=129 129+120-49=200
А+1,2а+1,3а=3,5а
Если а=20, то
20*3,5=70(книг) - всего
<span>
6a + 4b + 3b -8a= 6а-8а+4в+3в=7в-2а,
при a=1; b=0,5</span>
7*0,5-2*1=3,5-2=1,5
Ответ: 1,5