Problem Solving

If you know how to solve the following questions and you know how to explain your answers, please let me know. Thanks!
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1) When positive integer x is divided by positive y, the remainder is 9. If x / y = 96.12, what is the value of y?
a)96
b)75
c)48)
d)25
e)12

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2) If t = (1) / (2^9 * 5^3) is expressed as a terminating decimal, how many zeros will t have between the decimal point and the fist nonzero digit to the right of the decimal point?
a)Three
b)Four
c)Five
d)Six
e)Nine

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3) If x, y, and k are positive numbers such that (x / x+y)(10) + (y / x+y)(20) = k and if x<y, which of the following could be the value of k?

a)10
b)12
c)15
d)18
e)30

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4)For any positive integer n, the sum of the fist n positive integers equals (n(n+1)) / 2. What is the sum of all even integers between 99 and 301?
a)10,100
b)20,200
c)22,650
d)40,200
e)45,150