160= negre + colorate
colorate / 3 - 28 = negre
160 = colorate/3 -28 + colorate
160+28=colorate/3 + colorate(se aduc la acelasi numitor prin amplificare cu 3)
188=4 colorate / 3
colorate= 188*3/4 =>colorate= 47*3=141 creioane colorate
negre=141/3 - 28 = 47-28=19 creioane negre