0.19 for one cookie and 0.59 for one doughnut
x for how much one cookie costs and y for how much one doughnut costs
6x+4y=3.5
12x+5y=5.23
solve by substitution: (elimination would work too)
4y=3.5-6x
y=0.875-1.5x
12x+5(0.875-1.5x)=5.23
12x+4.375x-7.5x=5.23
4.5x=0.855
x=0.19
now use x to solve for y:
6(0.19)+4y=3.5
1.14+4y=3.5
2.36=4y
y=0.59
Check the work: 6(0.19)+4(0.59)=3.5
Answer: OPTION D: 
Step-by-step explanation:
By definiton, fractions have the following form:

Where "a" is called numerator and "b" is the denominator. The numerator and the denominator are Integers.
In order to solve this exercise you need to remember de Division of fractions:

In this case, according to the information given in the exercise, you know that
of rubies are divided into 4 lots.
Therefore, in order to calculate the weight in pounds of each lot, you need to divide
by 4.
Then, you get the following result:

As you can notice, this result matches with the Option D.
Answer:
The answer is B
Step-by-step explanation:
Its just B