Помогите решить систему номер 2

Решите задачу:

$\left \{ {{7x - 0,4y = -5} \atop {4x - 0,4y = 10}} \right. \\ \\ \left \{ {{7x - 0,4y = -5} \atop {- 4x + 0,4y = - 10}} \right. \\ \\ 3x = - 15\\ x = -5\\ \\ \left \{ {{x = -5} \atop {4 * (-5) - 0,4y = 10}} \right. \\ \\ \left \{ {{x = -5} \atop {- 20 - 0,4y = 10}} \right.\\ \\ \left \{ {{x = -5} \atop {- 0,4y = 30}} \right. \\ \\ \left \{ {{x = - 5} \atop {y = - 75 }} \right.$