Final answer:
To simplify the expression, combine the coefficients of the like terms and keep the variable and radical unchanged.
Step-by-step explanation:
To simplify the expression 10√2y + 5√2y + 3√2y, we can combine the like terms by adding their coefficients. The like terms in this expression are the terms with the same variable (y) and the same radical (√2).
When we add the coefficients (numbers in front of the square roots), we get 10 + 5 + 3 = 18. Therefore, the simplified expression is 18√2y. Option B - 18√2y - is the correct answer.