Kevin, Barbara, and their mother and father went backpacking in Yosemite National Park. On the first and second days, each hiker had a serving of food for
breakfast, lunch, and dinner. A large, noisy, brown bear barged into camp the
second night, got the food pack down from the tree where they had hung it, and
ate one half of the food that was left. The next morning, after they all had
breakfast, they found they had 4 food servings left. They decided they had better
hike back to their car. How many servings of food did they begin the trip with?

he used the algebra tiles correctly.

step-by-step explanation:

given : 3x(2x-1)

solution :

since he used algebra tiles .

armando's solution is the same in the solution shown in figure

as he distributed 2x into x and x and wrote them vertically

and also write   -1 vertically

and 3x into x and x and x and wrote it horizontally

performing the multiplication in the algebra tiles we get

and solving the given expression :

3x(2x-1)

since solving the expression using tiles   and solving the expression algebraically we get the same answer

thus   we can choose the first statement as the answer to this problem which is "he used the algebra tiles correctly".

d 600 because 15*10*2=300

300+300=600

step-by-step explanation: