Factorise 16x+28y The common thing between each number is 4, so you would put 4 on the outside of the brackets, and divide the numbers by 4 to do so e.g 16x÷4=4x 28y÷4=7y =4(4x+7y)
First you would find a common number to divide both sides by so 2 then you would set it up in a distributive for 2(3x+14y) when you distribute you get 16x+28y. I hope it helps