Решите любую букву, пожалуйста. ДАЮ 15 БАЛЛОВ!

$a)\; \left \{ {{5x-y=2} \atop {4x+2y=8|:2}} \right.\; \left \{ {{y=5x-2} \atop {2x+y=4}} \right. \; \left \{ {{y=5x-2} \atop {y=4-2x}} \right. \; \left \{ {{5x-2=4-2x} \atop {y=4-2x}} \right. \; \left \{ {{3x=6} \atop {y=4-2x}} \right. \\\\\left \{ {{x=2} \atop {y=4-2\cdot 2}} \right. \; \left \{ {{x=2} \atop {y=0}} \right. \; \; \to \; \; (2;0)$

в)

$\left \{ {{7x+2y=51|\cdot 3} \atop {5x-3y=1|\cdot 2}} \right. \; \left \{ {{21x+6y=153} \atop {10x-6y=2}} \right. \oplus \left \{ {{31x=155} \atop {5x-3y=1}} \right. \; \left \{ {{x=5} \atop {25-3y=1}} \right. \\\\\left \{ {{x=5} \atop {3y=24}} \right. \; \left \{ {{x=5} \atop {y=8}} \right. \; \; \to \; \; (5;8)$