1) the sum of x and its cube
x + x³ or x³ + x
2) the quotient of a number and five times the number
3) The difference between six times the number and y, where y is the larger number.
y - 6x
4) 20 more than the product of 15 and x
15x + 20
5) 15 less than the quotient of thrice the number and 5