(24t^2+8st)/(5s^2+15st ) = 8t*(3t + s) / 5s*(s + 3t) = 8t/5s, теперь подставим t=1/4; s=5/12 8*(1/4)/5*(5/12)=2/(5*(5/12))= (2/5)/(5/12)= (2*12)/(5*5)= 24/25 Ответ: 24/25.