The first green box: 2b+34<54 To solve this you subtract 34 from both sides. That leaves you to: 2b<20. Then you divide 2 to both sides. Which gets you: b<10.
The second green box: 2b-34<54 1. Add 34 to both sides. (2b<88) 2. Divide both sides by 2. (b<44)
The third green box: 2b+34>=54 1. Subtract 34 from both sides. (2b>=20) 2. Divide both sides by 2. (b>=10)
Fourth green box: 2b+34>54 1. Subtract 34 from both sides. (2b>20) 2. Divide both sides by 2. (b>10)