The sentence for the inequality is:
Three times a number w is less than 18
So we translate it in math terms:
three = 3
times = multiplication
a number = w (the letter they suggest)
less than = < (inequality symbol)
18 = 18
So this goes as:
3 w < 18
Which we can even solve for w by dividing both sides by the factor 3 that accompanies w:
w < 18/3