<span>1/5x + 7 = 17 - 1/20x
1/5x + 1/20x = 17 - 7
5/20x = 10
5 = 10 * 20x
5 = 200x
x = 5/200
x = 1/40
/ это знак деления
</span>
Ответ:
если не видно ответ 1 10/15
1)<span>1/12+3 4/15</span>=3+<span>1/12</span>+<span>4/15</span> = 3+<span>1·5/12·5</span>+<span>4·4/15·4</span>=3+<span>5/60</span>+<span>16/60</span>=3+ <span>5+1660</span>=3 <span>21/60</span>=3 <span>7·3/20·3</span>=3 <span>7/20</span> = 3.35
2)3 19/21+2 2/3=5+<span>19/21</span>+<span>2/3</span>=5+<span>19·1/21·1</span>+<span>2·7/3·7</span>=5+1<span>9/21</span>+<span>14/21</span>=5+ <span>19+14/21</span>=5 <span>33/21</span>=5 11·3/7·3=5 <span>11/7</span>=5 <span>4+1·7/7</span>=6 <span>4/7
</span>3)5*5 4/5=5·4+5·5/5=5<span>·</span><span>29/5</span> = <span>5·29/5</span> = <span>145/5</span> = <span>29·5/5</span><span> = 29
</span>И все в таком роде
4)<span>1 7/9*1 2/3=2 26/27
</span>5)<span>5 1/10-1 1/16=4 3/80
</span>6)<span>4-2/7=3 5/7
</span>7)<span>4/9+1 2/3=2 1/9
</span>8)5 3/8-2 11/16=2 11/16
Находим координаты векторов и их длины,затем длины приравниваем.