In the equation, you can see that 250 marbles are split between blue marbles and red marbles. The equation states that there are 24 more blue marbles than red marbles. So let x = the number of red marbles. Which means that x + x + 24 = 250 marbles.We can simplify this to 2x + 24 = 250. Subtract 24 from each side to get 2x = 226. Then divide by 2 on each side to get that there are 113 red marbles. The question asked for the number of blue marbles, so you add 24 to 113 to get 137 blue marbles. To check, you can add 137 + 113 and you will get 250.