408÷(2+3+5+7)=24

24×2=48

24×3=72

24×5= 120

24×7= 168

the second question

(X+2)+(X-2)+2X+X/2= 1296

X=288

288+2=290

288-2=286

288×2=576

288÷2= 144

Third question

Analysis: 900 meters apart, after a period of time, the two are 2700 meters apart. One possibility is that two people walk with their backs to each other. The second possibility is that they are in the same direction, but B is in front and A is behind.

The first solution:

(2700-900) ÷ (200+250) = 4 minutes

The second solution

(2700-900) ÷ (250-200) = 54 minutes