Упростите выражение: 2(a-3)+3a+b 4(0,3x-2y)+7,8x-y 3(2c-3d)+2(2,5c-d) 5(3x+y)+2(7x+12y)

1 ) 2 ( a - 3 ) + 3a + b = 2а - 6 + 3а + b = 5а - 6 + b;

2 ) 4 ( 0,3x - 2y ) + 7,8x - y = 1,2x - 8y + 7,8x - у = 9х - 8у - у = 9х - 9у = 9 ( x - y );

3 ) 3 ( 2c - 3d ) + 2 ( 2,5c - d ) = 6с - 9d + 5c - 2d = 11c - 9d - 2d = 11c - 11d = 11 ( c - d );

4 ) 5 ( 3x+y ) + 2 ( 7x + 12y ) = 15x + 5y + 14x + 24y = 29x + 5y + 24y = 29x + 29y = 29 ( x + y ).