1.) Let's say that the circle on the graph below represents x. The arrow is pointing to all the numbers greater than x, which happens to be on -2. If it points right, this means that x can equal to any number greater than -2. So your answer is x > -2.
2.) For inequalities such as these, you can simplify just like what you do for normal equations. Let's isolate x.

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Answer: 
Step-by-step explanation:
We know that the general form of the exponential decay formula is
, where y is final amount remaining after t time, A is the original amount and r is the rate of decay
Now, the ratio of strontium-90 remaining, p , as a function of years, t , since the nuclear accident. 
Hence, the ratio of remaining since the nuclear accident is 