please help me i feel clueless.

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write the sum or difference in simplest form.
1.on monday,cathy read 1/6 of her book,and on tuesday she read 2/6 of the book.how much has she read?

A.1/6
B.1/5
C.1/3
D.1/2
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2.jack has 4/8 of a pizza left from a party.if he eats another 1/8,how much is left?

A.3/8
B.2/3
C.5/8
D.1/2
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4.how much longer than 5/8 inch is 7/8 inch?

A.1 1/2
B.1/4
c.1 3/8
D.1 1/8 Inches
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5.plasma makes up 11/20 of your blood,and blood cells make up the other 9/20.how much more of your blood is plasma than blood cells?

A.1/20
b.1/10
c.1
D.11/20