I think it A... But if it not sorry I didn’t help... hope this is the answer I am sure it is...
The answer is 1/40.First you have to do 1/4 times 10 which you put over 1 so 1/4 times 10/1,than you flip one of the #'s so 1/4 times 1/10 which equals 1/40
5 because if you plug in to get the equation 3x+20=7x then subtract 3x from both sides and divide by 4 from both sides