Call the unknown number n. "Twice a number" tells us to multiply 2 times n. Now, add 4 to that product. That gives us this expression:
2n + 4
The result refers to the above sum, and it is greater than or equal to 8, which can be represented as algebraically as:
2n + 4 ≥ 8
To find the interval, let's first isolate the n-term by subtracting 4 from both sides
2n ≥ 4
Now, divide both sides by 2 to solve for n.
n ≥ 2 is the interval
To graph this on the number line, you would draw a closed circle at x = 2 and then shade everything to the right of 2 since as you move to the right on the positive side of the number line, the numbers get increasingly larger.
