Ten less than twice the product of s and t

Ten (10) less than (-) twice (2x) the product (x) of s and t.

The word 'product' tells you that you'll be multiplying. So, the product of s and t is st. Then, you need to multiply it by 2 (remember the twice than). Now, you have 2st. 'Less than' tells you that you're taking the first number (10) away from the second number (2st). So ten less than the product of s and t is 2st - 10.