The answer is the option C and the option D, which are:
C. Double the number of pages in the book.
D. The age of my friend.
The explanation for this problem is shown below:
By definition, a variable is an unkown quantity. In the Option A the quantity is given: 
seconds in a minute. In the option B you know the quantity too, which is 
years old. But the option C and the option D does not give any quantity, you don't know the number of pages in the book or the age of the friend yet. Therefore, the answer is the options C and D.
300*5=1500
150*5=750
75*5=375
2325
Answer:
Step-by-step explanation:
By solving given equations, the value of c is 30.
Given two equations
x + 2y = 10 and
3x + 6y = c
These lines represents the same line for some constant c.
Value of c:
x + 2y = 10-------------(1)
3x + 6y = c-------------(2)
Dividing equation (2) by 3
After solving the above equation, we get
x + 2y = c/3-----------(3)
Remember that a line is written as ax + by = c, in our case, both lines have a =1 and b = 2. Therefore, in orther that the two lines are equal, we need that, 10 = c/3
c = 10 × 3 = 30
c = 30
Therefore,
The value of c is 30.
Find out more information about equations here
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Answer:
y = 
Step-by-step explanation:
Squaring a number means multiplying the number by itself. 0*0=0. 1*1=1. 2*2=4, and 3*3=9. This is the pattern shown in the table.
