Will give no wrong answers as well! 50 points

To cancel out the X's find the least common multiple of 5 and 4:

 multiples of 5: 5, 10, 15, 20, 25, 30

multiples of 4: 4, 8, 12, 16, 20, 24

the least common multiple of 5 and 4 is 20, 
 so we need to multiply 5x and 4 x by numbers that would make-20 and 20 ( -20+20 = 0) which would cancel them out
 

5 x -4 = -20

4 x 5 = 20

-20 + 20 = 0  

the 3rd answer would cancel out the x's