Answer:
60
Step-by-step explanation:
divide 120 by 4 you get 30 then multiply 30 by 2
It's pretty simple! So it looks like you are learning proportions. You would cross multiply to achieve your answer.
First, let's do your first problem:
2 12
--- = ----
5 n
You would take 5 and multiply it by 12 and get 60! Then you would do the same with 2 times n, giving you 2n (because you do not know what n represents YET.)
Now you should have this:
60=2n OR 2n=60
We must isolate our variable, in order to do that, get rid of two! But how? You would do this by dividing 2n by 2. Yet in equations, when you do something to one side, you must do it to the other because they must be EQUAL! (hence the "equa-" in equation)
2n=60
--- ---
2 2 DIVIDE 2 into 60
----------
n= 30 Simplify!
Your final answer for the first question is n= 30!
Answer:

Step-by-step explanation:
3 envelopes having 2 red card
2 envelopes having 1 red card and 1 black card
1 envelope having 2 black cards
We are given that . An envelope is selected at random and a card is withdrawn and found to be red.
So, No. of ways of envelope having red card = 3+2 = 5
No. of required ways of envelope having 1 red card and 1 black card = 2
So, probability of getting an envelope having 1 red card and 1 black card = 
Hence The chance the other card is black is 
(16-x²)+(4-x) or (-x²+16)+(-x+4)
Combine like terms
(-x²+20-x) or (-x²-x+20)
The correct answer is 12
Set up a ratio and then solve. See paper attached. (: