Люди!! Хелпп!!5.79,5.80

[latex]5.79)\quad \left \{ {{7^{x+1}\cdot 2^{y}=4} \atop {y-x=3}} \right. \; \left \{ {{7^{x}\cdot 7\cdot 2^{x}\cdot 2^3=4} \atop {y=x+3}} \right. \; \left \{ {{14^{x}=\frac{1}{14}} \atop {y=x+3}} \right. \\\\ \left \{ {{14^{x}=14^{-1}} \atop {y=x+3}} \right. \; \left \{ {{x=-1} \atop {y=2}} \right. [/latex] [latex]5.80)\quad \left \{ {{(\frac{1}{3})^{x}\cdot 5^{y}=75} \atop {x+y=1}} \right. \; \left \{ {{3^{-x}\cdot 5\cdot 5^{-x}=3\cdot 5^2} \atop {y=1-x}} \right. \; \left \{ {{15^{-x}=15} \atop {y=1-x}} \right. \\\\ \left \{ {{-x=1} \atop {y=1-x}} \right. \; \left \{ {{x=-1} \atop {y=2}} \right. [/latex]