you can work this out by putting the ration in a column eg 2:7
and if you know how many spots are in one column like for the 2 in 2:7 has 114 spots then you need to find oht how many are in that 114! basically just do 114 ÷ 2 =72 then use 72 to multiply the 7 (in 2:7) by 72 which makes 504.
I THINK THIS IS THE ANSWERIM REALLY SORRY IF MY ANSWER TURNS OUT WRONG!!
First find out how much each bead costs. In this case, it is .24 (48/200=.24) Now you simply multiply .24 by 25, equaling 6. She will have to pay 6 more dollars.