Question Number 4690 by thachan last updated on 21/Feb/16
$${x}+{y}=\mathrm{67} \\ $$$${x}−{ay}=\mathrm{7} \\ $$
Answered by 123456 last updated on 21/Feb/16
$$−{x}+{ay}=−\mathrm{7} \\ $$$$\left({a}+\mathrm{1}\right){y}=\mathrm{60} \\ $$$${y}=\frac{\mathrm{60}}{{a}+\mathrm{1}} \\ $$$${x}=\mathrm{7}+{ay} \\ $$$${x}=\mathrm{7}+\frac{\mathrm{60}{a}}{{a}+\mathrm{1}} \\ $$$${x}=\frac{\mathrm{67}{a}+\mathrm{7}}{{a}+\mathrm{1}},{y}=\frac{\mathrm{60}}{{a}+\mathrm{1}} \\ $$$${x}+{y}=\frac{\mathrm{67}\left({a}+\mathrm{1}\right)}{{a}+\mathrm{1}}=\mathrm{67} \\ $$$${x}−{ay}=\frac{\mathrm{7}\left({a}+\mathrm{1}\right)}{{a}+\mathrm{1}}=\mathrm{7},{a}\neq−\mathrm{1} \\ $$