Remember that the < and > signs indicate whether something is greater than or less than something else. If you don't remember which is which, think of the symbol as an alligator—whichever way the open mouth is facing is the greater amount, because the alligator wants the bigger amount over the smaller amount.
In this case, you are given that 3 x [some number] < 1, or that 3 x [some number] is less than one. You must plug in a number that makes the left side of the sentence left than one.
To do this, you could use a negative number, such as -1, which would automatically make the product negative. You could also plug in a fraction that is smaller than 1/3, as 1/3 x 3 = 1.
So several answers that could complete this would be -1 and, say, 1/4.
