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
the answer is
9 blue cubes
11 red cubes