In this example, there are three people involved: Jessica and her two sisters. If Jessica and her two sisters are each able to save $21 a week, this means that they are able to save $63 a week in total:
3* 21 = 63
As they have four weeks, they will be able to make $252 in total:
63 * 4 = 252
This would be added to the amount that they have already saved, which is $225:
252 + 225 = 477
This means that they will not have enough money after 4 weeks.
after 4 weeks, they will have 21*4=$84 per kid (4 kids). Therefore we need to multiply this by 4. 84*4=$336. You must remeber that they started with $225, so 225+336=$561, which is more than $512, so they can pay for the trip!
