381= x+ (x+15) + (y-2) + y
y = [x+ (x+15) +(y-2)] / 2
rezulta 2y= 2x+15+y-2 => y= 2x+13
381 = x + (x+15) +(2x+13 -2)+ 2x+13
381 = 2x +15 + 2x + 13 -2 + 2x +13
381 = 6x +39 => 381-39 = 6x => x= 342/6 => x= 57
deci primul numar (57+15)=72, al doilea 57, al treilea(2*57+11)=125; al patrulea(2*57+13) = 127