Solving these is quite simple; think of "a number" as a value of either n or x (depending on personal preference) then just find the operations being done based on key words; 1. Sum= addition so it is x+5 2. Decrease= subtraction so it is 11-n 3. Quotient= division so it is -9/y 4. Twice= multiply by two, minus= subtract, so it is 2n-13