Wendy saved up for a family trip to the beach. for each $1 she saved, her parents pledged to save $5. if her parents were able to save $2, how much did wendy save?

225/5 = 45
This means the parents gave her five dollars forty five times. If they gave her a five every time she saved one dollar, you just have to multiply the money she saved each time and the number of times she saved it, and you'll get the answer. 
Wendy saved $45 by herself

$45.00. You set up a proportion. You put 1 on top of 5 and put x on top of 225. Once you do that, you multiply 225 by 1 to get 225 then divide it by 5 to get 45.
Example:
1/5      x/225
225 x 1=225
225/5= 45
Answer= $45.00

3were boys and 5 were girls