When i try to open up Minecraft it crashes and then says 'Minecraft could not continue as it has run out of memory' so i can't play on sandlot. If any one now how to fix it please tell me.
Did you try any of the fixes I sent you? You could also try removing your texture pack - You've got quite a high resolution pack on.
Move the pointer to the top left part of the tool bar. Click on the apple logo. Click on "About This Mac". Click on "More Info". This will tell you a lot about your Mac. Memory(RAM), CPUs, Hard drives, etc.
When you click on "About This Mac", a box should pop up with a big shiny apple. It will list processor, memory, and start up disk. What does it say on the Memory Line?
Ok. There is a memory part which says. Your Mac contains 4 memory slots, each of which accepts a 1600 MHz DDR3 memory module.
This probably has a factor in this problem. Resource packs do take up space. Like @Kyukuro said, a texture pack with high resolution would especially take up space. Hopefully this solution will help you.