Explanation:
Moving to the left of the number line means that the numbers are getting smaller, so with the example of
x < 3.5, x can be 3.4, 3.3, 3.2 and so on
Moving to the right of the number line means that the numbers are getting bigger, for example x > -1.5, x can be -1.4, -1.3, -1.2, -1.1, 0, 0.1, 0.2 and so on
x < 3.5 means that a number (x) is less than 3.5, so it's a hollow circle at 3.5 with the arrow to the left
x > -1.5 means that a number (x) is greater than -1.5, we cannot go the left of the number line as it will mean x is less than (<) -1.5, so it's a hollow circle at 1.5 with the arrow to the right
x ≥ -9/2 can be written as x ≥ -4.5 which means that a number (x) is greater than or equal to -4.5. It's a filled circle because you include -4.5 with the arrow to the right.
x ≤ 7/4 can be written as x ≤ 1.75 which means that a number (x) is less than or equal to 1.75, so it's a filled circle at 1.75 with the arrow to the left
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