4.

[tex]\displaystyle\bf\\\left \{ {{ \frac{2x + 1}{3} - \frac{10y + 11}{7} = 4 \: \: | \times 21 } \atop { \frac{x + 10}{2} - \frac{7y + 3}{5} = 8 \: \: | \times 10}} \right. \\ \displaystyle\bf\\\left \{ {{7(2x + 1) - 3(10y + 11) = 84} \atop {5(x + 10) - 2(7y + 3) = 80 }} \right. \\ \displaystyle\bf\\\left \{ {{14x + 7 - 30y - 33 = 84} \atop {5x + 50 - 14y - 6 = 80 }} \right. \\ \displaystyle\bf\\\left \{ {{14x - 30y = 110} \atop {5x - 14y = 36 }} \right. \\ \displaystyle\bf\\\left \{ {{7x - 15y = 55 \: \: | \times ( - 5) } \atop {5x - 14y = 36 \: \: | \times 7 }} \right. \\ \displaystyle\bf\\ + \left \{ {{ - 35x + 75y = - 275} \atop {35x - 98y = 252 }} \right. \\ \\ 75y - 98y = 252 - 275 \\ - 23y = - 23 \\ y = - 23 \div ( - 23 )\\ y = 1 \\ \\ 5x - 14 \times 1 = 36 \\ 5x = 36 + 14 \\ 5x = 50 \\ x = 5 0\div 5 \\ x = 10[/tex]

Ответ: ( 10 ; 1 )