What part of the mixture is alcohol? What FRACTION of the workers take their vacation?

3.) If 10 parts of alcohol is mixed with 15 parts of water, what part of the mixture is alcohol?
a. 2/3
b. 2/5
c. 1/3
d. 3/5

4.) If 2/5 of the workers in a factory go on vacation in September and 1/3 of the remainder takes their vacation in October, what fraction of the workers take their vacation in some other time?
a. 2/5
b. 1/3
c. 1/15
d. 4/15

[Skempurt]

Maam pa solve: What number must be added to each of the numbers 3, 4, 7, and 5 such that the sum of the square of the first two numbers is 65 less than twice the product of the last two numbers. Thank you po!