1. The expression (23,000 minus 789) multiplied by 19 can be described using words as "Nineteen times the result of subtracting 789 from 23,000".
2. The expression 2.6 plus 88 times 3 to the power of 3 can be described using words as "The sum of 2.6 and 88 times 3 raised to the third power".
3. The expression "Donald's score is less than twice Mary's score" would be written mathematically as D < 2M, where D represents Donald's score and M represents Mary's score.
4. The expression "The square of a number plus 5 times the number is equal to 24" would be written mathematically as x^2 + 5x = 24, where x represents the number.