View Compilation Error

0_0_27421485_18797.c: In function 'main':
0_0_27421485_18797.c:21:3: error: expected expression before '/' token
   //M = (a + b) * 7;
   ^
0_0_27421485_18797.c:22:3: error: expected expression before '/' token
   //n = n % M;
   ^