Which value of x satisfies the inequality x+3<20?

17

19

21

23

Neither actually, if 20 is bigger than x+3 nothing + 3 will give you something under 20. You could actually use 17 + 3 but, then again the sign would have to be = rather than <.

17 + 3 = 20

19 + 3 = 20

21 + 3 = 24

23 + 3 = 26