There are 7 boxes stacked on the floor in the math department supply closet. Each box has a height of 10 inches or 8 inches. The height of the stack of 7 boxes is 5 feet. How many boxes in the stack are 8 inches in height?

5 of the 7 boxes are 8 inches in height

Step-by-step explanation:

Mathematically;

1 ft = 12 inches

So, 5 ft will measure 5 * 12 = 60 inches

So from what we have ,

We want to combine 8 and 10 inches to give 60 inches total

Let the number of 10 inches be x and the number of 8 inches be y

Mathematically;

x + y = 7 •••••(i)

10x + 8y = 60 ••••(ii)

From equation i, x = 7-y

Put this in equation ii

10(7-y) + 8y = 60

70-10y + 8y = 60

70-60 = 10y-8y

2y = 10

y = 10/2

y = 5

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".

answer: x=60