The answer is
For the first equation, the sum has to be a positive number, so -5 has to muliply another negative number. So A & B are out.
Next we figure out if it's C or D.
-5 x -2 = 10
6 x 5 = 30
30 + 10 = 40
D isn't the answer because 6 x -2 is a negative number which won't get you 40.