If Harriet rolls the number cube 39 times, how many times can she expect to roll a 3 or 4?

13 times

Step-by-step explanation:

P(3 or 4) = 1/3, so she can expect to roll a 3 or 4 13 times

b

step-by-step explanation:

a difference is the result of subtraction. while each of these expressions has subtraction in it, a difference will be the result when subtraction is the last operation applied in the order of operations for the expression. this means subtraction must be outside of the parenthesis. only b has this.