If the angles of a quadrilateral are $\mathrm{x}°,(\mathrm{x}-10)°,(\mathrm{x}+30)° \mathrm{and} 2\mathrm{x}°$, then find the greatest angle.

Let's assume, 

$\angle \mathrm{A}=\mathrm{x}°, \angle \mathrm{B}=(\mathrm{x}-10)°,\angle \mathrm{C}=(\mathrm{x}+30)°,\angle \mathrm{D}=2\mathrm{x}°$.

According to the angle sum property of a quadrilateral: 

$\angle \mathrm{A}+\angle \mathrm{B}+\angle \mathrm{C}+\angle \mathrm{D}=360°$

$\mathrm{x}+\mathrm{x}-10+\mathrm{x}+30+2\mathrm{x}=360°$

$5\mathrm{x}+20°=360°$

$5\mathrm{x}=360°-20°=340°$

$\mathrm{x}=\frac{340°}{5}=68°$

$\angle \mathrm{A}=\mathrm{x}=68°$ 

$\angle \mathrm{B}=(\mathrm{x}-10)° =68°-10°=58°$

$\angle \mathrm{C}=(\mathrm{x}+30)°=68°+30°=98°$

$\angle \mathrm{D}=2\mathrm{x}=2\times 68°=136°$

Therefore, the greatest angle is $\angle \mathrm{D}=136°$.