1)(630+210):3*1=280
2)(705-245):10=46
1) (m:5+3)*6=46
(m/5 +3)*6=46
6m/5+18=46
6m+90=230
6m=230-90
6m=140
m=70/3
m=23 1/3 или m≈23,3
2)7*t-14=28
7t=28+14
7t=42
t=6
3)56:(36:r-2)=8
r≠18
r≠0
56:(36/r-2)=8
56:36-2r/r=8
56*r/36-2r=8
56*r/2(18-r)=8
28*r/2(18-r)=8
28*r/18-r=8
28r/18-r=8
28r=8(18-r)
28r=144-8r
28r+8r=144
36r=144
r=4
720/12=60 (руб) - заплатили за 1 метр голубой тесьмы.
Белая по той же цене. Значит: 60*3=180 (руб) заплатили за белую.
1)7ц7/30-(5ц11/30-у)=3ц19/30; (30*7+7/30)-[(30*5+11)/30-у]=(30*3+19)/30; 217/30-(161/30-у)=109/30; 217/30-161/30+у=109/30; 56/30+у=109/30; у=109/30-56/30; у=53/30; у=1ц23/30; проверка: 217/30-(161/30-53/30)=217/30-108/30=109/30=3ц19/30; 2)(х-1ц9/17)+2ц14/17=5ц5/17; [х-(1*17+9)/17]+(17*2+14)/17=(17*5+5)/17; (х-26/17)+48/17=90/17;
(Х-26/17)=90/17-48/17; (х-26/17)=42/17; х=42/17+26/17; х=68/17; х=4; проверка (68/17-26/17)+48/17=42/17+48/17=90/17=5ц5/17;