It seems that explanation of both 1) and 2) are not so good.
in equation x^2Y^3=200 we can find that (5^2)*(2^3)=200
- here is the point that x may be 5 or -5. Unless we can decide it, we can not solve the DS problem.
Y is positive since 200 is positive.
1) we are given that y is an integer- tells us nothing,
x*y=-10 or X*y=10 - not sufficient
- tells that either both x and y are positive or negative. We know that y is positive so x - must be positive, thus we can find the value of x*y.
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