Without experience that would help you recognize it right away, I think
you would just need to try numbers until you find it.
Pick a number, multiply it by itself with pencil and paper, and see if it works.
(2)² = 4 too small
(3)² = 9 too small, and not growing fast enough; this could take all day
(10)² = 100 still too small
(15)² = 225 oops, too big; go back down
(12)² = 144 too small
(14)² = 196 too big
(13)² = 169 just right; hope the bears don't come back too soon
x has to equal 1. 3/10 + 1/5 = 1/2
the equation is now 1/2 + x = 1 1/2x
x = 1
1 1/2 = 1 1/2
Answer:
4
Step-by-step explanation:
5-1=4
Answer: Choice D

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Explanation:
The left portion is the interval (-∞, -2)
This is a shorthand way of saying 
The curved parenthesis says "do not include this endpoint as part of the solution set". Note the open hole at x = -2 in the diagram.
In contrast, the value x = 4 is included (due to the filled in circle), so we use a square bracket for this endpoint. Therefore, the right-hand portion is represented by [4, ∞) which translates to 
Negative and positive infinity will always use a parenthesis, and never a square bracket. This is because we can only approach infinity but never reach it, so we cannot include it as an endpoint.
All of this builds up to the full interval notation to be 
The only square bracket is near the 4; everything else is a curved parenthesis. This is why choice D is the final answer.