Hi !
The volume of the cube is :
18 × 18 × 18= 5 832 mm³
The answer is D.
Ralph is 12. If Ralph is 12 that means Sara is 4 (12/4=3). In 4 years Sara will be 8 and Ralph would be 16 (16/8=2).
the question in English
Juan has blue cubes with a 55 mm edge and red cubes with a 45 mm edge. He stacks them in two columns, one of each color; he wants the two columns to be the same height. How many cubes does he need, as a minimum, of each color?
Let
x---------> the number of blue cubes
y--------> the number of red cubes
we know that
Juan wants that the two columns to be the same height
so

solve for y

I proceed to calculate a table, assuming values of x to calculate the value of y. When the values of x and y are whole numbers, I will have found the solution.
the table in the attached figure
therefore
<u>the answer is</u>
9 blue cubes
11 red cubes