Twenty percentages of the staff at a certain hospital have unlisted telephone numbers. 60% and 40% of this person are males and females respectively. You select 300 names randomly from the hospital phone book. How many Females can be expected to have unlisted phone numbers?

24 females with unlisted phone numbers

Step-by-step explanation:

20% of the staff at this hospital have unlisted telephone numbers

40% of the staff at the hospital that have unlisted telephone numbers are females

This means that 40% of the 20% of the 300 names in the phone book will be females with unlisted phone numbers.

1/5 (20%) of 300 is 60, and 40% of these 60 people is 24.

There are 24 females in this 300 with unlisted phone numbers.

I'm not entirely sure if this is what you were asking, since you had some errors in your question.

Multiply the second equation by 3, so 4x-y=6 becomes 12x-3y=18.

x + 3y = -5
+ (12x-3y = 18)

13x = 13

So x = 1

Plug x = 1 into any of these, such as 1 + 3y = -5, which becomes 3y = -6, and then y = -2.
x = 1
y = -2