this is the answer of your problem, but I believe that you must study in your book
|2s-7|<1
case 1
2s-7 >0
2s>7
s>7/2
there fore
2s-7 < 1
2s<8
s < 4
0 1 2 3 4 5
____l__l__l__l__l__l_____________
l l
the solution are [3.5 , 4]
it finds the other interval