help .ican't edit e.g.sdcard pormission

I'root my chinese tablet and i'can't chang e.g.pormission from (ro) to (rw)
My tablet

Device: Polaroid MID0734
Android: 4.2.2
CPU Max Frequency: 999 Mhz
CPU Cores: 2
GPU: Broadcom VideoCore IV HW
System RAM: 449 MB
Display: 800x480 (6.94")

SYSTEM

Model: MID0734
Manufacturer: Polaroid
Android: 4.2.2
API Level: 17
Kernel: 3.4.5(eng.gfs.20130930.151321)
Compilation: MID0734-V1.0-2013.09.03
Uptime: 00:00:21:14

PROCESSOR

Processor: ARMv7 Processor rev 0 (v7l)
Number of Cores: 2
Max Frequency: 999 Mhz
Current Frequency: 312 Mhz
CPU Usage: 31.2 %
Instruction Sets: armeabi-v7a, armeabi

GRAPHICS PROCESSING UNIT

General Info:

Model: VideoCore IV HW
Vendor: Broadcom
OpenGL Version: OpenGL ES 2.0

Advanced Info:

Viewport Size: 2048 x 2048
Renderbuffer Size: 2048 x 2048
Cubemap Size: 2048 x 2048
Texture Size: 2048 x 2048
Texture Units: 2048
Vertex Textures: 2048
Combined Textures: 2048
Vertex Attributes: 2048
Vertex Uniforms: 2048
Varying Vectors: 2048
Fragment Uniform Vectors: 2048
Extensions:
GL_EXT_debug_marker GL_OES_compressed_ETC1_RGB8_texture GL_OES_compressed_paletted_texture GL_OES_texture_npot GL_ARB_texture_non_power_of_two GL_OES_EGL_image GL_OES_EGL_image_external GL_EXT_discard_framebuffer GL_OES_query_matrix GL_OES_framebuffer_object GL_OES_rgb8_rgba8 GL_OES_depth24 GL_OES_depth32 GL_OES_stencil8 GL_OES_packed_depth_stencil GL_OES_draw_texture GL_EXT_texture_format_BGRA8888 GL_APPLE_rgb_422 GL_OES_matrix_palette

MEMORY

System Memory:

Total System RAM: 449 MB
Free System RAM: 77 MB
Java VM Max Memory: 48 MB

Storage Space:

Internal: 1004 MB (277 MB Free)
External: 15228 MB (11849 MB Free)

Eney one can help me?
Thank's