Let me tell you the meaning of these keys first.
MC =It will clear the memory and set its value to 0
MR =It will help you to recall the value the value stored in memory.
MS =It will help you to store a value in the memory of your calculator.
M+ =It takes the number on the display and add it to the stored value.

Let me give you a simple example.
5 x 5 = 25 (on display)
MS (stores 30 in memory)
12 x 3 = 36 (on display)
M+ (takes 36, adds it to 25, stores result 61 in memory)
3 x 7 = (21)
M+ (takes 61, adds 21, stores the result 82)
MR (displays the result 82)

Let me tell you the meaning of these keys first.
MC =It will clear the memory and set its value to 0
MR =It will help you to recall the value the value stored in memory.
MS =It will help you to store a value in the memory of your calculator.
M+ =It takes the number on the display and add it to the stored value.

Let me give you a simple example.
5 x 5 = 25 (on display)
MS (stores 30 in memory)
12 x 3 = 36 (on display)
M+ (takes 36, adds it to 25, stores result 61 in memory)
3 x 7 = (21)
M+ (takes 61, adds 21, stores the result 82)
MR (displays the result 82)