book Maths Puzzle Numerical Ability

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-2/3(6/5-7/10)=17/20

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book Other Question

State the axiom which justifies each of the following:
a) (3)(4)=(4)(3)
b) (3+4)+5=3+(4+5)
c) If 3 =x, then x = 3
d) 2(3+x)= 6 + 2x
i am having problems with the slopes in graphing equations. i have
(4,5) (2,3)
m=3-52-4 = -2-2
now i am suppose to write weather the line is vertical or horizontal....how do