Gọi 2 số cần tìm là a; b[tex]\Rightarrow \left\{\begin{matrix} a+b=76\\a+2,5b=21 \end{matrix}\right.[/tex]
[tex]\Rightarrow \left\{\begin{matrix} a+b=76\\1,5b=-55 \end{matrix}\right.[/tex]
[tex]\Rightarrow \left\{\begin{matrix} a+b=76\\b=\frac{-110}{3} \end{matrix}\right.[/tex]
[tex]\Rightarrow \left\{\begin{matrix} a=\frac{338}{3}\\b=\frac{-110}{3} \end{matrix}\right.[/tex]