In the box, there were red, blue and black pens. 70% of the pens were black pens. The number of red pens was $$\frac{4}{5}$$ of the number of blue pens. Find the ratio of the number of black pens to the number of red pens to the number of blue pens. Give your answer in simplest form. <br> <input min="0" type="number" id ="imp5pg185q15_1" class="lineinput" placeholder="?" /> : <input min="0" type="number" id ="imp5pg185q15_2" class="lineinput" placeholder="?" /> : <input min="0" type="number" id ="imp5pg185q15_3" class="lineinput" placeholder="?" />