The main idea is the number of marbles and the denominator of the probability. All you have to do is multiply the fraction by a fraction which is equal to 1 which makes the denominator equal to 63. We know 63 is a multiple of 9. 9 goes 7 times in 63 so we multiple the fraction [tex]\frac{2}{9}[/tex] with [tex]\frac{7}{7}[/tex] which gives, [tex]\frac{2 * 7}{9 * 7}[/tex] which when evaluated gives [tex]\frac{14}{63}[/tex] and the numerator is the number of red marbles in the bag. So there are 14 red marbles in the bag :D
