Verified Answer :

"is" means equals
"of" means multiply
let "what number" be represented by "x"

so we get the equation: 
12 = 1/3 x  [solve for x]
x = 12
3    [multiplied 3 to both sides]
x = 36    [<- answer]


121/3

 Multiply across which is 123=36

Answer: 36