Answerit's not 20, because 20 is the sum, and difference is subtraction, and product is multiplication.
6x2x2
first do 20 times 20 then double the answer
20,110,25,4
37 x 2
How about: 8*9 = 72
20(6)
Is { 0, 20 } closed under multiplication
How about: 4*5 = 20 as one example
If a number is divisible by both 4 and 5, it's divisible by 20.
1 x 20 = 20 2 x 10 = 20 4 x 5 = 20
As a product of its prime factors: 2*2*5 = 20 or as 22*5 = 20