Сумма 6 и 8 членов арифметической прогрессии равна 16, а сумма 5 и 11 ее членов равна 18....

Решите задачу:

$\left \{ {{a_6+a_8=16} \atop {a_5+a_{11}=18}} \right. \\\\ \left \{ {{a_1+5d+a_1+7d=16} \atop {a_1+4d+a_1+10d=18} \right. \\\\ \left \{ {{2a_1+12d=16} \atop {2a_1+14d=18} \right. \\\\ \left \{ {{2a_1+12d=16} \atop {2d=2} \right. \\\\ \left \{ {{2a_1+12d=16} \atop {d=1} \right. \\\\ \left \{ {{2a_1+12=16} \atop {d=1} \right. \\\\ \left \{ {{2a_1=4} \atop {d=1} \right. \\\\ \left \{ {{a_1=2} \atop {d=1} \right.$