The total amount of marbles before drawing a marble is 2+3=5. There are 2 red marbles. Thus, the theoretical probability of drawing a red marble from the bag is 2/5.
If you keep the red marble, there are now 4 total marbles in the bag. There is also only 1 remaining red marble. Thus, the theoretical probability of drawing a red marble is now 1/4.
Her work is incorrect because she accidentally changed -14 to -7 in the second step. Working it out from the top we get (x-14)+11=x-(x-4) x-14+11=x-x+4 x-3=0+4 Final answer: x=7 Hope I helped :)
