50 take away what equals 20?
If we start with 50 and we’re left with 20, how many did we take away? We could calculate the missing number by subtracting the 20 from 50 to tell us how much will be left. 50 has five tens and 20 has two tens. Five tens take away two tens is three tens, which is 30.
50 take away 30 equals 20. The missing number is 30.