Write an algebraic expression to model the unknown number situation. the sum of a number and one-third A 1-column table with 5 rows. Column 1 is labeled Addition Words with entries add, increase by, more than, sum, total. Which statements are true? Select all that apply. You can replace "a number" with a variable to represent an unknown value. You can replace "sum" with an addition sign. You can replace "sum" with an multiplication sign. You can replace "one-third" with One-third. The correct algebraic expression is One-third n