Make 2 equations from the question first
x is the number of pints for type 1
y is the number of pints for type 2
The equation
x + y = 120
60% x + 85% y = 65% (x + y)
Solve the equation
From the 2nd equation
0.6x + 0.85y = 0.65(x + y)
0.6x + 0.85y = 0.65x + 0.65y
0.85y - 0.65y = 0.65x - 0.6x
0.2y = 0.05x
y = 4x
From the 1st equation
x + y = 120
x + 4x = 120
5x = 120
x = 24
y = 4x
y = 96
The first type should be 24 pints, the second type should be 96 pints

Length of each side of each of these three equilateral triangle is :
Solution is in attachment ~
Answer: a. n= 1068
b. n= 164
Step-by-step explanation:
The formula to find the sample size :

, where p=prior population proportion , z* = critical z-value and E = Margin of error.
Here , let p=proportion of computers that use a new operating system.
Given : Confidence level = 95%
i.e. z* = 1.96 [by z-table]
Margin of error : E = 3% =0.03
a. If p is unknown , then we assume p=0.5
Then, 
i.e. n= 1068
b. p=0.96
Then, 
i.e. n= 164.