Final answer:
Using the associative property in mathematics, the expression equivalent to (13+15+20)+(20+47+18) is (13+15)+(20+20+47+18), which corresponds to option b.
Step-by-step explanation:
The associative property in mathematics states that when adding or multiplying numbers, the way in which the numbers are grouped does not affect the sum or product. In other words, if you have a sum like (a + b) + c, it's equivalent to a + (b + c). Similarly, for multiplication, (a * b) * c is equal to a * (b * c). This property allows us to move parentheses in expressions with more than two terms.
To find an expression equivalent to the given expression (13+15+20)+(20+47+18) using the associative property, we can regroup the numbers without changing their order. The correct expression using the associative property is (13+15)+(20+20+47+18), which corresponds to option b.