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% by volume is an expression of concentration that says the volume of solute (alcohol) per unit volume of solution (alcohol + water). 

In this case, your unit of volume is mL so that 25 % v/v of alcohol solution means you have 25 mL of alcohol for every 100 mL of alcohol solution. 

Let x be the volume of alcohol in 200 mL of 25 % v/v alcohol solution, 

25 mL alcohol/100 mL alcohol solution = x mL alcohol/200 mL alcohol solution 

x mL alcohol = (0.25)(200) = 50 mL 

It is very easy!! :D
Maybe for you it's very easy, I'm only gr. 7 -_- btw, thanks but please don't be big headed
Btw, I think it's wrong? can you explain where 25% came? and also it's asking for alcohol and water right?

P.S. Not demanding, just curious
Oh sorry for being big headed.... 25%.... Well i made it like that just for a sample solution... it's up to you in your solution..... That's how i make my answers.... so they can learn to solve but in the same know how to do it.... :D
ok then, thank you again :) it helped me