Question 1144740
Ben has some marbles. 4/7 of the marbles are red and the rest are blue. If he has 18 blue marbles, how many marbles does Ben have altogether ? 
<pre>With {{{4/7}}} being red, {{{matrix(1,3, 1 - 4/7, or, 3/7)}}} is blue.
We then get the following PROPORTION, with T being the total number of marbles: {{{matrix(1,3, (3/7)/1, "=", 18/T)}}}     
{{{matrix(1,3, 3T/7, "=", 18)}}} ------ Cross-multiplying
3T = 7(18) ----- Cross-multiplying
T, or total number of marbles = {{{highlight_green(matrix(1,5, 7(18)/3, "=", 7(cross(18))6/cross(3), "=", 42))}}}