The "MRC" function on a calculator is short for "Memory Recall." When you use the separate "Memory" button to store a particular number in your calculator's memory, you use the MRC button to bring that stored number back up on screen. This is particulalrly handy when you're using the same number in several different calculations. You can set up and use the MRC function on any calculator in just a few seconds.
Input the number you want to save to memory into your calculator using the number keys.
Press the "Memory Input" button on your calculator. Depending on the manufacturer of your calculator this button may be labeled "M+" or "Min." The number on screen will be saved to memory.
Continue to use your calculator as normal. Perform any necessary calculators that are required until you get to the point where you need to recall the number you saved to memory in Step 2.
Press the "MRC" or "Memory Recall" button. The number you saved to the memory in Step 2 will now be displayed on your calculator's screen.